US20180182854A1 - Semiconductor device, method for manufacturing semiconductcor device, and electronic device - Google Patents
Semiconductor device, method for manufacturing semiconductcor device, and electronic device Download PDFInfo
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- US20180182854A1 US20180182854A1 US15/798,843 US201715798843A US2018182854A1 US 20180182854 A1 US20180182854 A1 US 20180182854A1 US 201715798843 A US201715798843 A US 201715798843A US 2018182854 A1 US2018182854 A1 US 2018182854A1
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- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/189—High frequency amplifiers, e.g. radio frequency amplifiers
- H03F3/19—High frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
- H03F3/195—High frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only in integrated circuits
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- H03—ELECTRONIC CIRCUITRY
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- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
- H03F3/213—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only in integrated circuits
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- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
- H03F3/245—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages with semiconductor devices only
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- H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
- H01L2223/58—Structural electrical arrangements for semiconductor devices not otherwise provided for
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- H01L2223/6683—High-frequency adaptations for monolithic microwave integrated circuit [MMIC]
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- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/02—Bonding areas; Manufacturing methods related thereto
- H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
- H01L2224/06—Structure, shape, material or disposition of the bonding areas prior to the connecting process of a plurality of bonding areas
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- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/42—Wire connectors; Manufacturing methods related thereto
- H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
- H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
- H01L2224/481—Disposition
- H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
- H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
- H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
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- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/42—Wire connectors; Manufacturing methods related thereto
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- H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
- H01L2224/48257—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a die pad of the item
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- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/495—Lead-frames or other flat leads
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- H01L23/49562—Geometry of the lead-frame for devices being provided for in H01L29/00
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- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
- H01L2924/181—Encapsulation
Definitions
- the embodiments discussed herein are related to a semiconductor device, a method for manufacturing a semiconductor device, and an electronic device.
- Two known technologies for reducing the parasitic capacitance generated in a semiconductor device are a technology where the permittivity of an insulating layer that covers a gate electrode or wiring is reduced and a technology where an insulating layer that covers a gate electrode or wiring is provided with a cavity (space) surrounding the gate electrode or wiring.
- a semiconductor device including: a substrate; a first conductor provided on the substrate; a first insulating layer which is provided on the substrate, covers the first conductor, and has a cavity that surrounds the first conductor; and a second insulating layer which is provided on the first insulating layer and has an opening at a position corresponding to the cavity.
- FIG. 1 depicts one example of a semiconductor device
- FIG. 2 depicts a first example configuration of a semiconductor device according to a first embodiment
- FIGS. 3A to 3C depict a cavity and an opening according to the first embodiment
- FIG. 4 depicts a second example configuration of a semiconductor device according to the first embodiment
- FIGS. 5A to 5C are first diagrams depicting a method for forming a semiconductor device according to a second embodiment
- FIGS. 6A to 6C are second diagrams depicting a method for forming a semiconductor device according to the second embodiment
- FIGS. 7A and 7B are third diagrams depicting a method for forming a semiconductor device according to the second embodiment
- FIGS. 8A and 8B are fourth diagrams depicting a method for forming a semiconductor device according to the second embodiment
- FIGS. 9A and 9B depict a first example configuration of a semiconductor device according to a third embodiment
- FIGS. 10A and 10B depict a second example configuration of a semiconductor device according to the third embodiment
- FIGS. 11A to 11C are first diagrams depicting an example of a method for forming a semiconductor device according to a fourth embodiment
- FIGS. 12A and 12B are second diagrams depicting an example of a method for forming a semiconductor device according to the fourth embodiment
- FIGS. 13A to 13C depict a different example of a method for forming a semiconductor device according to the fourth embodiment
- FIGS. 14A to 14C depict a different example of a method for forming a semiconductor device according to the fourth embodiment
- FIGS. 15A and 15B depict a different example of a method for forming a semiconductor device according to the fourth embodiment
- FIGS. 16A and 16B depict one example of a semiconductor device according to a fifth embodiment
- FIGS. 17A to 17C depict (a first part of) a method for forming a semiconductor device according to the fifth embodiment
- FIGS. 18A to 18C depict (a second part of) a method for forming a semiconductor device according to the fifth embodiment
- FIG. 19 depicts one example of a semiconductor package according to a sixth embodiment
- FIG. 20 depicts one example of a power factor correcting circuit according to a seventh embodiment
- FIG. 21 depicts one example of a power supply apparatus according to an eighth embodiment.
- FIG. 22 depicts one example of an amplifier according to a ninth embodiment.
- FIG. 1 depicts one example of a semiconductor device.
- FIG. 1 schematically depicts a principal part of this example of a semiconductor device in cross section.
- a semiconductor device 600 depicted in FIG. 1 is equipped with a high electron mobility transistor (HEMT) 610 .
- HEMT high electron mobility transistor
- a compound semiconductor layer 620 including a channel layer (electron transit layer), a spacer layer, an electron supply layer, a cap layer, and the like is used in the semiconductor device 600 .
- a gate electrode 611 of the HEMT 610 is provided together with a pair of electrodes 612 and 613 in an active region defined by an element isolation region 621 of the compound semiconductor layer 620 .
- the electrode 612 is used as a source electrode or a drain electrode of the HEMT 610 and is connected to (the electron supply layer of) the compound semiconductor layer 620 .
- the electrode 613 is used as the drain electrode or the source electrode of the HEMT 610 and is connected to (the electron supply layer of) the compound semiconductor layer 620 .
- An insulating layer 630 is formed using silicon nitride (SiN), silicon oxide (SiO 2 ), or the like in the active region, and the gate electrode 611 passes through the insulating layer 630 and is connected to (the cap layer of) the compound semiconductor layer 620 .
- the gate electrode 611 whose cross-sectional form is T-shaped is illustrated.
- the HEMT 610 is covered with an insulating layer 631 that uses a material with a relatively low permittivity, such as a so-called “Low-k material”.
- the insulating layer 631 has a cavity 631 a that surrounds the gate electrode 611 .
- an insulating layer 632 which uses a material with a relatively high permittivity such as SiN, is provided on the insulating layer 631
- an insulating layer 633 which uses a material with a relatively low permittivity such as a Low-k material, is further provided on the insulating layer 632 .
- an insulating layer 634 which uses a material with a relatively high permittivity, such as SiN, is provided on the insulating layer 633 .
- a material with a relatively high permittivity such as SiN
- silsesquioxane As the material with a relatively high permittivity used in the insulating layer 631 and the insulating layer 633 , it is possible to use silsesquioxane.
- This material has a cage-like molecular structure, so that holes due to the molecular structure are formed inside the insulating layer 631 and the insulating layer 633 formed using silsesquioxane. That is, the insulating layer 631 and the insulating layer 633 are porous layers.
- Contacts 640 a , 640 b , 640 c are provided so as to pass through the insulating layer 634 , the insulating layer 633 , the insulating layer 632 , the insulating layer 631 , and the insulating layer 630 .
- Wiring 650 a that is connected to the contact 640 a and the contact 640 c and wiring 650 b that is connected to the contact 640 b are provided on the insulating layer 634 .
- the contact 640 a and the wiring 650 a are connected to the electrode 612 of the HEMT 610 and the contact 640 b and the wiring 650 b are connected to the electrode 613 of the HEMT 610 .
- the contact 640 c which is joined to the electrode 612 of the HEMT 610 via the wiring 650 a and the contact 640 a , is connected for example to conductors (not illustrated), such as vias and backside electrodes provided on the compound semiconductor layer 620 .
- a passive element for example, a capacitor 660
- a capacitor 660 is mounted together with the HEMT 610 on the compound semiconductor layer 620 of the semiconductor device 600 .
- a capacitor 660 which is configured by sandwiching a part of the insulating layer 632 that has a relatively high permittivity between a lower electrode 661 and an upper electrode 662 , is provided on the compound semiconductor layer 620 .
- HEMI have superior high-speed characteristics and are used in the signal processing circuits of optical communication systems and other high-speed digital circuits.
- HEMI have excellent low-noise characteristics, they are expected to be utilized in amplifiers for microwave and millimeter wave bands.
- fT current gain cutoff frequency
- gm transconductance
- a cavity 631 a is provided in the insulating layer 631 covering the HEMI 610 at a part that surrounds the gate electrode 611 , the parasitic capacitance generated between the gate electrode 611 and other conductors is reduced compared to a configuration where an insulating material (Low-k material, SiN, or the like) is provided at the same part.
- an insulating material Low-k material, SiN, or the like
- the insulating layer 632 and the insulating layer 633 for example are further provided on top of the insulating layer 631 that covers the HEMI 610 and has the cavity 631 a which surrounds the gate electrode 611 .
- a material with a relatively low permittivity such as a Low-k material
- a material with a relatively high permittivity such as SiN
- the insulating layer 632 that uses a material with a relatively high permittivity, such as SiN, may be used for example as a hard mask when etching the insulating layer 631 that uses a material with a relatively low permittivity, such as a Low-k material, and/or may be used as a dielectric of the capacitor 660 in the MMIC. This means that it is difficult to produce an MMIC semiconductor device 600 with a configuration that does not include the insulating layer 632 .
- the following method is used to form the cavity 631 a .
- a sacrificial layer (filler) that uses a material that decomposes under light, such as ultraviolet rays, is formed on the insulating layer 630 above the compound semiconductor layer 620 in which the HEMT 610 is formed, so as to cover the gate electrode 611 .
- the porous insulating layer 631 is formed on this sacrificial layer.
- irradiation with light such as ultraviolet rays, is performed to cause decomposition and gasification of the sacrificial layer surrounding the gate electrode 611 .
- the components of the gasified sacrificial layer are removed through the holes in the porous insulating layer 631 . By removing the sacrificial layer, the cavity 631 a is formed so as to surround the gate electrode 611 .
- an insulating layer 632 formed using a material with a relatively high permittivity, such as SiN is a denser film than the porous insulating layer 631 that has a relatively low permittivity.
- the configurations given in the following embodiments are used to realize semiconductor devices that each have a cavity that surrounds the gate electrode.
- FIG. 2 depicts a first example configuration of a semiconductor device according to the first embodiment.
- FIG. 2 schematically depicts a principal part of the first example configuration of a semiconductor device according to the first embodiment in cross section.
- a semiconductor device 1 A depicted in FIG. 2 includes a compound semiconductor layer 20 and a HEMT 10 formed using the compound semiconductor layer 20 .
- the compound semiconductor layer 20 includes an electron transit layer 20 c , a spacer layer 20 d, an electron supply layer 20 e, and a cap layer 20 f that are stacked on a semiconductor substrate 20 a , such as silicon carbide (SiC), with a buffer layer 20 b in between.
- a semiconductor substrate 20 a such as silicon carbide (SiC)
- SiC silicon carbide
- the HEMT 10 When the HEMT 10 is configured as a GaN-type HEMT, where gallium nitrogen (GaN) and aluminum gallium nitrogen (AlGaN) are used as materials, the following structure is used for example as the compound semiconductor layer 20 .
- i-type GaN layers i-GaN
- An i-type AlGaN layer i-AlGaN
- An n-type AlGaN layer is used for the electron supply layer 20 e.
- An n-type GaN layer (n-GaN) is used for the cap layer 20 f.
- two-dimensional electron gas (2 DEG) is formed in the vicinity of the upper surface of the electron transit layer 20 c.
- a gate electrode 11 of the HEMT 10 and a pair of electrodes 12 and 13 are provided in an active region defined by an element isolation region 21 of the compound semiconductor layer 20 .
- the electrode 12 is used as a source electrode or a drain electrode of the HEMT 10
- the electrode 13 is used as a drain electrode or a source electrode of the HEMT 10 .
- the electrode 12 and the electrode 13 are connected (ohmically connected) to the electron supply layer 20 e of the compound semiconductor layer 20 .
- Both the electrodes 12 and the electrode 13 are made of metal materials, such as titanium (Ti) or aluminum (Al).
- An insulating layer 30 is formed using SiN or the like in the active region.
- the cap layer 20 f of the compound semiconductor layer 20 , and the electrode 12 and the electrode 13 are covered by the insulating layer 30 .
- the gate electrode 11 passes through the insulating layer 30 and is connected to the cap layer 20 f.
- the gate electrode 11 whose cross-sectional form is T-shaped is illustrated.
- Metal materials, such as nickel (Ni) and gold (Au), are used for the gate electrode 11 .
- the HEMT 10 is covered with an insulating layer 31 that uses a material with a relatively low permittivity, such as a Low-k material.
- the insulating layer 31 has a cavity 31 a that surrounds the gate electrode 11 .
- the insulating layer 32 that uses a material with a relatively high permittivity, such as SiN is provided on the insulating layer 31
- an insulating layer 33 that uses a material with a relatively low permittivity, such as a Low-k material is further provided on the insulating layer 32 .
- an insulating layer 34 that uses a material with a relatively high permittivity, such as SiN, is provided on the insulating layer 33 .
- Silsesquioxane for example, methyl silsesquioxane
- This material has a cage-like molecular structure, so that holes due to the molecular structure are formed inside the insulating layer 31 and the insulating layer 33 that are formed using this material. That is, the insulating layer 31 and the insulating layer 33 are porous layers.
- a contact 40 a , a contact 40 b , and a contact 40 c are provided so as to pass through the insulating layer 34 , the insulating layer 33 , the insulating layer 32 , the insulating layer 31 , and the insulating layer 30 .
- Wiring 50 a connected to the contact 40 a and the contact 40 c and wiring 50 b connected to the contact 40 b are provided on the insulating layer 34 .
- a contact that passes through the insulating layer 34 , the insulating layer 33 , the insulating layer 32 , the insulating layer 31 and the insulating layer 30 and is connected to the gate electrode 11 , and wiring connected to this contact are additionally provided.
- the contact 40 a and the wiring 50 a are connected to the electrode 12 of the HEMT 10
- the contact 40 b and the wiring 50 b are connected to the electrode 13 of the HEMT 10
- the contact 40 c which is joined to the electrode 12 of the HEMT 10 via the wiring 50 a and the contact 40 a , is connected to conductors (not illustrated), such as vias and backside electrodes provided on the compound semiconductor layer 20 .
- Conductors not illustrated
- Metal materials such as titanium tungsten (TiW) and Au, are used for the contact 40 a and the wiring 50 a , and also the contact 40 b and the wiring 50 b .
- metal materials are used for the other conductors, such as the contact 40 c.
- a passive element such as a capacitor 60
- the capacitor 60 which is configured by sandwiching a part of the insulating layer 32 that has a relatively high permittivity between a lower electrode 61 and an upper electrode 62 , is provided on the compound semiconductor layer 20 .
- an opening 80 is provided at a position corresponding to the cavity 31 a of the insulating layer 31 so as to pass through the insulating layer 32 , the insulating layer 33 , and the insulating layer 34 .
- the semiconductor device 1 A is constructed so that the insulating layer 32 (and the insulating layer 34 ) that has a relatively high permittivity is partially removed from above (at least part of) the cavity 31 a of the insulating layer 31 .
- the parasitic capacitance generated between the gate electrode 11 positioned inside the cavity 31 a and other conductors, for example, the electrode 12 , the electrode 13 , or the contact 40 a or the contact 40 b connected to the electrodes 12 and 13 is reduced.
- the cavity 31 a is provided so as to surround the gate electrode 11 and the insulating layer 32 , which has a relatively high permittivity, is removed by the opening 80 from above the cavity 31 a , so that the generation of parasitic capacitance is suppressed.
- the characteristics, such as the high-frequency characteristics, of the semiconductor device 1 A due to parasitic capacitance is suppressed.
- the part of the insulating layer 32 remaining after the part above the cavity 31 a has been removed may be used as a hard mask or may be used as the dielectric of the capacitor 60 .
- FIGS. 3A to 3C depict the cavity and the opening according to the first embodiment.
- FIGS. 3A to 3C schematically depict, when looking from the insulating layer 32 side, example planar layouts of principal parts of the HEMT 10 described above and the insulating layer 31 and the insulating layer 32 (and the insulating layers 33 and 34 ) provided on top of the HEMT 10 .
- the electrodes 12 and 13 that each function as a source electrode or a drain electrode are provided on two sides of the gate electrode 11 .
- the contact 40 d is connected to the gate electrode 11
- the contact 40 a and the contact 40 b are respectively connected to the electrode 12 and the electrode 13 .
- the cavity 31 a of the insulating layer 31 that covers the gate electrode 11 is provided so as to surround the gate electrode 11 .
- a configuration where the cavity 31 a is provided in a region between the electrode 12 and the electrode 13 and encloses part of the gate electrode 11 is illustrated in the drawings.
- the opening 80 is provided in the insulating layer 32 above the insulating layer 31 at a position corresponding to the cavity 31 a of the insulating layer 31 .
- the opening 80 corresponding to the cavity 31 a may be formed in a size that is the same or similar to the cavity 31 a when looking from above.
- the opening 80 provided corresponding to the cavity 31 a may be formed larger than the cavity 31 a when looking from above with a size that overlaps and encloses the entire cavity 31 a . Since it is possible, when an opening 80 of this size is provided, to increase the size of the region where the insulating layer 32 with a relatively high permittivity is not present above the cavity 31 a , it is possible to effectively reduce the parasitic capacitance caused by the insulating layer 32 .
- the size of the opening 80 is made larger than the cavity 31 a , it is possible to increase the efficiency of removal of the sacrificial layer when forming the cavity 31 a using a method, described later, that gasifies and removes the sacrificial layer by photodecomposition.
- the opening 80 provided corresponding to the cavity 31 a may be produced in a size that is smaller than the cavity 31 a and overlaps part of the cavity 31 a when looking from above. Since it is possible, even when an opening 80 of this size is provided, to provide a region where the insulating layer 32 with a relatively high permittivity is not present above the cavity 31 a , it is possible to reduce the parasitic capacitance due to the insulating layer 32 .
- the removal efficiency of the sacrificial layer may fall when forming the cavity 31 a using a method that gasifies and removes a sacrificial layer by photodecomposition as described later.
- the region where the cavity 31 a is disposed is not limited to this.
- the cavity 31 a may be provided so as to extend outside the electrode 12 and the electrode 13 , and may be provided so as to incorporate the entire gate electrode 11 . It is possible to provide the opening 80 corresponding to the cavity 31 a in keeping with the examples in FIGS. 3A to 3A based on the disposed region of the cavity 31 a and with consideration to the layout of the contacts 40 a to 40 d and the like and the layout of the wiring 50 a , 50 b , and the like (which are not illustrated in FIGS. 3A to 3C ) connected to the contacts 40 a to 40 d and the like.
- FIG. 4 depicts a second example configuration of a semiconductor device according to the first embodiment.
- FIG. 4 schematically depicts a principal part of the second example configuration of the semiconductor device according to the first embodiment in cross section.
- a semiconductor device 1 B depicted in FIG. 4 differs from the semiconductor device 1 A described above by having a configuration where the opening 80 provided corresponding to the cavity 31 a is filled with an insulating layer 35 .
- a material such as a Low-k material, with a relatively low permittivity that is lower than the material, such as SiN, used for the insulating layer 32 is used as the insulating layer 35 that fills the opening 80 .
- silsesquioxane such as methyl silsesquioxane may be used.
- holes due to the cage-like molecular structure of the material are formed inside of the insulating layer 35 to be formed. That is, the insulating layer 35 is a porous layer.
- this material for the insulating layer 35 generation of parasitic capacitance due to the insulating portion provided above the cavity 31 a is suppressed.
- resistance to moisture is increased, so that penetration of moisture into the cavity 31 a and the HEMT 10 and deterioration in the characteristics of the HEMT 10 due to moisture are suppressed.
- the insulating layer 35 that fills the opening 80
- a material with relatively high transmittance of light such as ultraviolet rays
- a relatively low density such as a porous layer
- the insulating layer 35 that fills the opening 80 may have a single-layer structure but may alternatively have a laminated structure where one or two or more insulating layers with a relatively low permittivity are laminated. Also, the insulating layer 35 that fills the opening 80 may have a laminated structure provided with one or two or more insulating layers with a relatively low permittivity on the lower side and with one or two or more insulating layers with a relatively high permittivity on the upper side. Even when a layer with a relatively high permittivity is provided on the upper side, so long as this is distant from the gate electrode 11 , generation of parasitic capacitance due to this layer with a relatively high permittivity is suppressed.
- the HEMT 10 in the semiconductor device 1 A and the semiconductor device 1 B described above is not limited to the GaN-based HEMT described earlier which uses GaN and AlGaN as materials, and it is possible to configure a HEMT using other materials.
- the HEMT 10 it is possible to configure a GaN-type HEMI that uses GaN and indium aluminum nitride (InAlN) as materials or a GaN-type HEMI that uses GaN and indium aluminum gallium nitrogen (InAlGaN) as materials.
- a GaN-type HEMI that uses GaN and InAlN i-GaN is used for the electron transit layer 20 c of the compound semiconductor layer 20 , i-InAlN for the spacer layer 20 d, n-InAlN for the electron supply layer 20 e, and n-GaN is used as the cap layer 20 f.
- i-GaN is used for the electron transit layer 20 c of the compound semiconductor layer 20
- i-InAlGaN is used for the spacer layer 20 d
- n-InAlGaN is used for the electron supply layer 20 e
- n-GaN is used for the cap layer 20 f.
- HEMI 10 aside from the various GaN-type HEMI described above, it is possible to configure an indium phosphorus (InP) type HEMI or the like.
- InP indium phosphorus
- the second embodiment is described as an example of a method for forming the semiconductor device 1 A and the semiconductor device 1 B described in the first embodiment.
- FIGS. 5A to 8B depict a method for forming a semiconductor device according to the second embodiment.
- FIGS. 5A to 5C , FIGS. 6A to 6C , FIGS. 7A and 7B , and FIGS. 8A and 8B schematically depict a principal part at each step in the method for forming a semiconductor device according to the second embodiment in cross section.
- the compound semiconductor layer 20 (substrate) on which the HEMI 10 and the like have been formed is prepared.
- a buffer layer 20 b and an electron transit layer 20 c of i-GaN, a spacer layer 20 d of i-AlGaN, an electron supply layer 20 e of n-AlGaN, and a cap layer 20 f of n-GaN are laminated in that order on a semiconductor substrate 20 a of SiC or the like by MOVPE (Metal Organic Vapor Phase Epitaxy) for example to form the compound semiconductor layer 20 .
- MOVPE Metal Organic Vapor Phase Epitaxy
- the element isolation region 21 is formed by ion implantation of argon (Ar), for example.
- the electrode 12 and the electrode 13 that are respectively used as a source electrode or a drain electrode are formed on the electron supply layer 20 e.
- a resist with an opening in a region where the electrode 12 and the electrode 13 are to be formed is formed on the cap layer 20 f of the compound semiconductor layer 20 using a photolithography technique.
- dry etching for example dry etching using a chlorine-based gas
- the cap layer 20 f exposed to the opening in the resist is removed.
- the metal material that forms the electrode 12 and the electrode 13 for example a Ti film and an Al film, is laminated and deposited on the entire surface, that is, on the upper surface of the resist and in the opening, and the Ti film and the Al film deposited on the upper surface of the resist are removed together with the resist (this method is called “lift-off”).
- a Ti film and an Al film are formed on regions of the electron supply layer 20 e of the compound semiconductor layer 20 where the electrode 12 and the electrode 13 are to be formed.
- a heat treatment for example a heat treatment in a nitrogen atmosphere at a temperature of 400 to 1000° C., is performed. By performing this heat treatment, the electrode 12 and the electrode 13 that are ohmically connected to the electron supply layer 20 e are formed.
- an insulating layer 30 (protective layer) that covers the cap layer 20 f, the electrode 12 , and the electrode 13 is formed on the compound semiconductor layer 20 .
- an SiN layer is formed by a CVD (Chemical Vapor Deposition) method.
- the gate electrode 11 that passes through the insulating layer 30 and is connected to the cap layer 20 f is formed.
- a resist with an opening in a region where the gate electrode 11 (for example, the leg portion of the T-shaped gate electrode 11 ) is to be formed is formed on the insulating layer 30 using a photolithography technique.
- the insulating layer 30 exposed to the opening of the resist is removed by dry etching, for example dry etching using sulfur hexafluoride (SF 6 ) gas, with the resist as a mask.
- the resist is removed and a resist with an opening in a region that includes the region where the gate electrode 11 is to be formed is newly formed.
- a metal material that forms the gate electrode 11 for example an Ni film and an Au film, is laminated and deposited on the entire surface, that is, on the upper surface of the newly formed resist and inside the opening, and after this, the resist is removed together with the Ni film and Au film deposited on the upper surface (this method is called “lift-off”).
- this method is called “lift-off”.
- the compound semiconductor layer 20 on which the HEMI 10 and the like have been formed is obtained.
- a sacrificial layer 90 is formed on the compound semiconductor layer 20 on which the HEMI 10 and the like have been formed.
- the sacrificial layer 90 a material that decomposes under light, such as ultraviolet rays, is used.
- an organic layer that includes a functional group containing oxygen (carbonyl group (CO), carboxyl group (COOH), hydroxyl (OH), or the like) and is decomposed by ultraviolet rays with a wavelength of 300 to 400 nm is used as the sacrificial layer 90 .
- a functional group containing oxygen carbonyl group (CO), carboxyl group (COOH), hydroxyl (OH), or the like
- ultraviolet rays with a wavelength of 300 to 400 nm
- methyl glutarimide polymethyl methacrylate, polypropylene, and polycarbonate may be given as examples of this type of organic layer.
- the material described above is formed by spin coating, for example, on the compound semiconductor layer on which the HEMT 10 has been formed to form the sacrificial layer 90 .
- the formed sacrificial layer 90 is patterned using a photolithography technique and an etching technique so as to remain in a predetermined region (or “disposed region”).
- the sacrificial layer 90 is patterned so as to remain in a region which, when viewed from above, is located between the electrode 12 and the electrode 13 and incorporates part or all of the gate electrode 11 .
- the sacrificial layer 90 is patterned so as to remain in a region which, when viewed from above, incorporates part or all of the gate electrode 11 and also incorporates part or all of the electrode 12 and part or all of the electrode 13 .
- the insulating layer 31 , the insulating layer 32 , the insulating layer 33 , and the insulating layer 34 are formed.
- the insulating layer 31 is formed using a material with a relatively low permittivity so as to cover the sacrificial layer 90 .
- a porous layer is formed as the insulating layer 31 .
- the insulating layer 32 is formed using a material with a relatively high permittivity on the formed insulating layer 31 .
- an SiN layer is formed as the insulating layer 32 .
- the insulating layer 32 is used as the dielectric of the capacitor 60 provided on the compound semiconductor layer 20 .
- the lower electrode 61 is formed in advance in a region where the capacitor 60 is to be formed before formation of the insulating layer 32 , and after formation of the insulating layer 32 , the upper electrode 62 that faces the lower electrode 61 with the insulating layer 32 in between is formed, thereby forming the capacitor 60 .
- the insulating layer 33 is formed using a material with a relatively high permittivity on the formed insulating layer 32 .
- a porous layer is formed as the insulating layer 33 .
- the insulating layer 34 is then formed, using a material with a relatively high permittivity for example, on the formed insulating layer 33 .
- an SiN layer is formed as the insulating layer 34 .
- a contact hole 41 a and a contact hole 41 b that respectively reach the electrode 12 and the electrode 13 are formed.
- a contact hole that reaches the gate electrode 11 is also formed together with the contact hole 41 a and the contact hole 41 b.
- the contact 40 a , the contact 40 b , and the like After formation of the contact hole 41 a , the contact hole 41 b , and the like, as depicted in FIG. 6B , the contact 40 a , the contact 40 b , and the like, and conductors such as the wiring 50 a , the wiring 50 b that are connected to the contacts 40 a , 40 b , and the like are formed.
- a metal material for example a TiW film and an Au film, that forms the seed layer for plating, described later, is formed by sputtering on the entire surface, that is, on the upper surface of the insulating layer 34 and the inner surfaces of the contact hole 41 a and the contact hole 41 b .
- a resist with openings in regions where the wiring 50 a , the wiring 50 b , and the like are to be formed is formed on the seed layer, and a wiring metal material, for example an Au film, that forms the wiring 50 a , 50 b , and the like is deposited on the seed layer by electroplating using the seed layer as a feeding layer.
- the resist is removed and the seed layer that is exposed after removal of the resist is removed by etching.
- the contact 40 a that is connected to the electrode 12 the wiring 50 a connected to the contact 40 a , the contact 40 b that is connected to the electrode 13 , and the wiring 50 b connected to the contact 40 b are formed.
- the contact connected to the gate electrode 11 and the wiring connected to this contact are formed.
- the opening 80 that passes through the insulating layer 34 , the insulating layer 33 , and the insulating layer 32 is formed as depicted in FIG. 6C .
- the insulating layer 34 , the insulating layer 33 , and the insulating layer 32 are removed in a region corresponding to the sacrificial layer 90 formed by patterning so as to keep the predetermined disposed region mentioned above, that is, a region that overlaps all or part of the sacrificial layer 90 when looking from above, thereby forming the opening 80 .
- the insulating layer 34 , the insulating layer 33 , and the insulating layer 32 are removed using a photolithography technique and an etching technique. As one example, a resist with an opening in a predetermined region is formed, the insulating layer 34 is removed by etching using the resist as a mask, and the insulating layer 33 and the insulating layer 32 are then removed in that order.
- the etching conditions (etching gas, etching time, and the like) of the insulating layer 34 , the insulating layer 33 , and the insulating layer 32 are set based on the materials used for each layer, the thicknesses, and the like.
- the sacrificial layer 90 under the insulating layer 31 is removed to form the cavity 31 a.
- light such as ultraviolet rays that pass through the insulating layer 31
- the sacrificial layer 90 decomposes due to the incident light and is gasified.
- the components of the gasified sacrificial layer 90 are discharged to outside the insulating layer 31 through the holes in the porous insulating layer 31 . By doing so, the cavity 31 a is formed in the insulating layer 31 .
- the insulating layer 32 and the insulating layer 34 that use SiN or the like have a property of relatively low transmittance for light such as ultraviolet rays. Since the insulating layer 32 , the insulating layer 33 , and the insulating layer 34 present on the insulating layer 31 , which include the insulating layer 32 and the insulating layer 34 with the property described above, are removed from above the sacrificial layer 90 , it becomes easier for light such as ultraviolet rays to reach the sacrificial layer 90 , which improves the efficiency of decomposition and gasification of the sacrificial layer 90 .
- the insulating layer 32 and the insulating layer 34 that use SiN or the like have a further property of being relatively dense films. Since the insulating layer 32 , the insulating layer 33 , and the insulating layer 34 on the insulating layer 31 , which include the insulating layer 32 and the insulating layer 34 with this further property, are removed from above the sacrificial layer 90 , it becomes easier for the gasified sacrificial layer 90 to be discharged to outside the insulating layer 31 , which improves the efficiency of removal of the sacrificial layer 90 .
- the opening 80 above the sacrificial layer 90 it is possible to form a stable cavity 31 a where the sacrificial layer 90 does not remain under the insulating layer 31 , that is, where the sacrificial layer 90 is prevented from remaining as residue around the gate electrode 11 .
- the semiconductor device 1 A since the insulating layer 32 and the insulating layer 34 of SiN or the like that have a relatively high permittivity are removed from above the cavity 31 a and the sacrificial layer 90 is prevented from remaining as residue around the gate electrode 11 in the cavity 31 a , generation of parasitic capacitance caused by these layers is suppressed. By doing so, the semiconductor device 1 A, for which deterioration in the characteristics due to parasitic capacitance is suppressed, is realized.
- the semiconductor device 1 B (see FIG. 4 ) is obtained.
- the opening 80 is filled by spin coating or the like with a material that has a lower permittivity than the material, such as SiN, used for the insulating layer 32 .
- the semiconductor device 1 B With the semiconductor device 1 B, by filling the opening 80 with the insulating layer 35 , the resistance to moisture is improved. By doing so, the semiconductor device 1 B, in which penetration of moisture into the cavity 31 a and the HEMI 10 and resulting deterioration in the characteristics of the HEMI 10 are suppressed, is realized.
- the step of filling the opening 80 with the insulating layer 35 is not limited to being performed after formation of the cavity 31 a and may be performed before the formation of the cavity 31 a.
- the opening 80 is filled with the insulating layer 35 as depicted in FIG. 8A without removing the sacrificial layer 90 .
- the sacrificial layer 90 is removed to form the cavity 31 a .
- a porous material with a relatively high transmittance of light such as ultraviolet rays and a relatively low density is used.
- a step (called “back grinding”) of grinding the back surface of the compound semiconductor layer 20 may be performed.
- Other processes may also be performed, such as formation of vias that pass through the compound semiconductor layer 20 after grinding and are connected to conductors (for example, the contact 40 c ) on the wiring layer side and formation of electrodes on the back surface of the compound semiconductor layer 20 after grinding.
- formation of the cavity 31 a (see FIG. 7A or 8B ) or both formation of the opening 80 (see FIG. 6C ) and formation of the cavity 31 a (see FIG. 7A or FIG. 8B ) may be performed after the back grinding.
- FIGS. 9A and 9B depict a first example configuration of a semiconductor device according to the third embodiment.
- FIG. 9A schematically depicts a principal part of the first example configuration of the semiconductor device according to the third embodiment in cross section.
- FIG. 9B schematically depicts the planar layout of a principal part of the first example configuration of the semiconductor device according to the third embodiment. Note that FIG. 9A is a schematic cross-sectional view corresponding to the position of a line L 9 -L 9 in FIG. 9B .
- the cavity 31 a provided in the insulating layer 31 that covers the gate electrode 11 is formed so as to extend to the positions of (the contact 40 a and the contact 40 b connected to) the electrode 12 and the electrode 13 respectively used as a source electrode and a drain electrode.
- the opening 80 is provided in the insulating layer 32 (and the insulating layer 33 and the insulating layer 34 ) on the insulating layer 31 corresponding to this cavity 31 a .
- the semiconductor device 1 C differs from the semiconductor device 1 A described above in this respect.
- the opening 80 provided corresponding to the cavity 31 a is provided above the cavity 31 a while avoiding the wiring 50 a and the wiring 50 b connected to the contact 40 a and the contact 40 b .
- the insulating layer 32 with a relatively high permittivity that remains above the HEMT 10 is reduced, which reduces the parasitic capacitance caused by the insulating layer 32 .
- a semiconductor device 1 C where deterioration in the characteristics due to parasitic capacitance is suppressed is realized.
- FIGS. 10A and 10B depict a second example configuration of a semiconductor device according to the third embodiment.
- FIG. 10A schematically depicts a principal part of the second example configuration of the semiconductor device according to the third embodiment in cross section.
- FIG. 10B schematically depicts the planar layout of a principal part of the second example configuration of the semiconductor device according to the third embodiment. Note that FIG. 10A is a schematic cross-sectional view corresponding to the position of a line L 10 -L 10 in FIG. 10B .
- the cavity 31 a provided in the insulating layer 31 that covers the gate electrode 11 is formed so as to extend to positions outside (the contact 40 a and the contact 40 b connected to) the electrode 12 and the electrode 13 respectively used as the source electrode or the drain electrode.
- the opening 80 is provided in the insulating layer 32 (and the insulating layer 33 and the insulating layer 34 ) on the insulating layer 31 corresponding to this cavity 31 a .
- the semiconductor device 1 D differs from the semiconductor device 1 A described above in this respect.
- the opening 80 provided corresponding to the cavity 31 a is provided above the cavity 31 a while avoiding the wiring 50 a and the wiring 50 b connected to the contact 40 a and the contact 40 b .
- the insulating layer 32 with a relatively high permittivity that remains above the HEMI 10 is reduced, which reduces the parasitic capacitance caused by the insulating layer 32 .
- a semiconductor device 1 D where deterioration in the characteristics due to parasitic capacitance is suppressed is realized.
- planar forms of the openings 80 in the semiconductor device 1 C and the semiconductor device 1 D are not limited to the examples described above. It is possible to set the planar form of the opening 80 based on the layout of the cavity 31 a , as well as the contact 40 a and the contact 40 b and the wiring 50 a and the wiring 50 b connected to the contacts 40 a and 40 b.
- the openings 80 in the semiconductor device 1 C and the semiconductor device 1 D may be filled with the insulating layer 35 which uses a material with a lower permittivity than the material, such as SiN, used for the insulating layer 32 .
- the semiconductor device 1 C and the semiconductor device 1 D by appropriately changing the disposed region of the sacrificial layer 90 (see FIG. 5B ) and the disposed region of the opening 80 (see FIG. 6C ) in accordance with the example method for forming described in the second embodiment.
- FIGS. 11A to 11C and FIGS. 12A and 12B depict an example of a method for forming a semiconductor device according to the fourth embodiment.
- FIGS. 11A to 11C and FIGS. 12A and 12B schematically depict a principal part in each step in the method for forming a semiconductor device according to the fourth embodiment in cross section.
- an opening 80 that passes through the insulating layer 34 , the insulating layer 33 , and the insulating layer 32 is formed.
- the opening 80 is formed in a predetermined region by using a photolithography technique and an etching technique according to the example steps depicted in FIG. 6C described above.
- the sacrificial layer 90 below the insulating layer 31 is removed to form the cavity 31 a .
- the cavity 31 a is formed in accordance with the example steps in FIG. 7A described above by decomposing and gasifying the sacrificial layer 90 via irradiation with light, such as ultraviolet rays, and discharging the components of the gasified sacrificial layer 90 to outside the insulating layer 31 through the holes in the porous insulating layer 31 .
- the opening 80 is filled with the insulating layer 35 that uses a material with a lower permittivity than the material, such as SiN, used for the insulating layer 32 .
- the sacrificial layer 90 may be removed through the holes in the insulating layer 31 and the insulating layer 35 to form the cavity 31 a.
- the contact 40 a , the contact 40 b , and the like and the wiring 50 a , the wiring 50 b and the like connected to the contacts 40 a , 40 b and the like are formed. This is performed in accordance with the example steps in FIGS. 6A and 6B described above.
- the semiconductor device 1 B may be obtained using this method.
- the wiring 50 c may be formed separate from the wiring 50 a , the wiring 50 b , and the like. Alternatively, the wiring 50 c may be connected to or integrally formed with one of the wiring 50 a , the wiring 50 b , and the like. Since it is possible to also form the wiring 50 c on top of the insulating layer 35 that fills the opening 80 , it is possible to increase the freedom with which the wiring is laid out in a semiconductor device 1 B a.
- back grinding when back grinding is performed on the compound semiconductor layer 20 , after back grinding, formation of the cavity 31 a or both formation of the opening 80 and formation of the cavity 31 a may be performed. In this way, when back grinding is performed in a state where the cavity 31 a is yet to be formed (i.e., where the sacrificial layer 90 is formed), it is possible to effectively suppress peeling of the layers near the cavity 31 a due to force and/or heat applied during back grinding.
- the insulating layers provided on the compound semiconductor layer 20 are not limited to the insulating layers 30 to 35 described above. As one example, it is possible to produce a structure formed using the method depicted in FIGS. 13A to 15B described below.
- FIGS. 13A to 15B depict different examples of methods of forming a semiconductor device according to the fourth embodiment.
- FIGS. 13A to 13C , FIGS. 14A to 14C , and FIGS. 15A and 15B schematically depict a principal part at each step in other example methods of forming a semiconductor device according to the fourth embodiment in cross section.
- steps up to the formation of the insulating layer 34 are performed first and then as depicted in FIG. 13A , formation of an insulating layer 36 with a relatively low permittivity and an insulating layer 37 with a relatively high permittivity is performed.
- the opening 80 that passes through from the insulating layer 37 as far as the insulating layer 32 is formed, and by irradiating with light, such as ultraviolet rays, as depicted in FIG. 13C , the sacrificial layer 90 is removed through the porous insulating layer 31 to form the cavity 31 a.
- the insulating layer 36 that has a relatively low permittivity and the insulating layer 37 that has a relatively high permittivity are formed.
- an opening 82 that passes through the insulating layer 37 and the insulating layer 36 is formed, and the opening 82 is filled with a porous insulating layer 38 that has a relatively low permittivity (as one example, an insulating layer 38 whose porosity is equal to or higher than the insulating layer 31 and the insulating layer 35 ).
- the sacrificial layer 90 is removed through the porous insulating layer 31 and the insulating layer 38 to form the cavity 31 a .
- the structure depicted in FIG. 15A is obtained by removing the sacrificial layer 90 to form the cavity 31 a and then filling the opening 80 with the insulating layer 35 , or alternatively by filling the opening 80 with the insulating layer 35 and then removing the sacrificial layer 90 to form the cavity 31 a .
- an insulating layer 39 with higher resistance to moisture than the insulating layer 35 is formed in a region that includes an area above the insulating layer 35 that fills the opening 80 .
- the insulating layer 39 with high resistance to moisture that is formed on the insulating layer 35 may have a higher permittivity than the insulating layer 31 and the insulating layer 35 , since the insulating layer 39 is further from the gate electrode 11 than the insulating layer 32 , it is possible to suppress the generation of parasitic capacitance due to the insulating layer 39 .
- FIGS. 13A to 13C It is possible to obtain a semiconductor device using methods like those depicted in FIGS. 13A to 13C , FIGS. 14A to 14C , and FIGS. 15A and 15B .
- MMIC semiconductor device it is possible to make various changes to the composition and structure of the insulating layers provided on the compound semiconductor layer 20 , and by appropriately changing the steps in keeping with such changes, it is possible to provide the opening 80 and the like and the cavity 31 a .
- FIGS. 16A and 16B depict one example of a semiconductor device according to the fifth embodiment.
- FIGS. 16A and 16B schematically depict a principal part of the semiconductor device according to the fifth embodiment in cross section.
- a semiconductor device 1 E depicted in FIG. 16A and a semiconductor device 1 F depicted in FIG. 16B are each equipped with a substrate 100 , which includes transistors (semiconductor elements) formed on a semiconductor substrate and one or two or more wiring layers, and a wiring layer 110 provided on the substrate 100 .
- the wiring layer 110 includes wiring 111 and wiring 112 , an insulating layer 113 that covers the wiring 111 and the wiring 112 , and an insulating layer 114 and an insulating layer 115 provided on top of the insulating layer 113 .
- the wiring 111 and the wiring 112 may be wiring on which electrical signals of different potentials are supplied or may be wiring on which electrical signals of the same potential are supplied.
- a material, such as a Low-k material, with a relatively low permittivity is used as the insulating layer 113 .
- the insulating layer 113 has a cavity 113 a that surrounds the wiring 111 and the wiring 112 .
- the insulating layer 113 includes the cavity 113 a that surrounds one out of the wiring 111 and the wiring 112 (in the illustrated example, the wiring 111 ).
- the wiring layer 110 is provided with an opening 120 that passes through the insulating layer 114 and the insulating layer 115 above the insulating layer 113 , which covers the wiring 111 and the wiring 112 and includes the cavity 113 a that surrounds one or both of the wiring 111 and the wiring 112 , at a position corresponding to the cavity 113 a.
- contacts that are joined to other wiring are connected to the wiring 111 and the wiring 112 , for example by passing through the insulating layer 115 , the insulating layer 114 , and the insulating layer 113 .
- the wiring layer 110 of the semiconductor device 1 E and the semiconductor device 1 F is constructed so that the insulating layer 114 that has a relatively high permittivity is partially removed from above (at least part of) the cavity 113 a of the insulating layer 113 .
- the parasitic capacitance generated between the wiring 111 and the wiring 112 positioned inside the cavity 113 a or between the wiring 111 and other conductors is reduced, so that deterioration in the characteristics, such as the high frequency characteristics, is suppressed.
- FIGS. 17A to 17C and FIGS. 18A to 18C depict a method for forming a semiconductor device according to the fifth embodiment.
- FIGS. 17A to 17C and FIGS. 18A to 18C schematically depict a principal part at each step in the method for forming a semiconductor device according to the fifth embodiment in cross section.
- the wiring 111 and the wiring 112 are formed on the substrate 100 .
- a sacrificial layer 130 is formed so as to cover the wiring 111 and the wiring 112 .
- a material that decomposes due to light such as ultraviolet rays, is used as the sacrificial layer 130 .
- the sacrificial layer 130 is formed in a predetermined region (or “disposed region”), for example a region that incorporates part or all of the wiring 111 and the wiring 112 , using a photolithography technique and an etching technique.
- the insulating layer 113 is formed using a material with a relatively high permittivity so as to cover the sacrificial layer 130
- the insulating layer 114 is formed using a material with a relatively low permittivity on top of the insulating layer 113
- the insulating layer 115 is formed using a material with a relatively low permittivity on the insulating layer 114 .
- the opening 120 that passes through the insulating layer 115 and the insulating layer 114 is formed.
- the opening 120 is formed in a region corresponding to the sacrificial layer 130 , that is, a region that entirely or partially overlaps the sacrificial layer 130 when looking from above.
- the sacrificial layer 130 below the insulating layer 113 is removed to form the cavity 113 a .
- light such as ultraviolet rays
- components of the sacrificial layer 130 produced by the resulting decomposition and gasification of the sacrificial layer 130 are discharged to the outside through the holes in the insulating layer 113 to form the cavity 113 a in the insulating layer 113 .
- a semiconductor device 1 E like that depicted in FIG. 16A described above is obtained.
- a semiconductor device 1 F like that depicted in FIG. 16B described above is obtained.
- the opening 120 above the sacrificial layer 130 By forming the opening 120 above the sacrificial layer 130 to partially remove the insulating layer 114 that has a relatively high permittivity, it is possible to sufficiently irradiate the sacrificial layer 130 with light, such as ultraviolet rays, and form a stable cavity 113 a where the sacrificial layer 130 is prevented from remaining as residue under the insulating layer 113 .
- light such as ultraviolet rays
- the opening 120 may be filled with a porous insulating layer 116 which uses a material with a lower permittivity than the material used for the insulating layer 114 .
- a porous insulating layer 116 which uses a material with a lower permittivity than the material used for the insulating layer 114 .
- the opening 120 is filled with the porous insulating layer 116 , and then the sacrificial layer 130 is removed through the insulating layer 113 and the insulating layer 116 to form the cavity 113 a.
- semiconductor devices 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, and the like are also possible to use the semiconductor devices 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, and the like as described above in the first to fifth embodiments in various electronic devices.
- Example applications in a semiconductor package, a power factor correction circuit, a power supply device, and an amplifier are described below as sixth to ninth embodiments.
- FIG. 19 depicts one example of a semiconductor package according to the sixth embodiment.
- FIG. 19 schematically depicts a principal part of one semiconductor package according to the sixth embodiment in plan view.
- a semiconductor package 200 depicted in FIG. 19 includes a lead frame 210 on which the semiconductor device 1 A described in the first embodiment, for example, is mounted, and resin 220 that seals the lead frame 210 and the semiconductor device 1 A.
- the semiconductor device 1 A is mounted on die pads 210 a of the lead frame 210 using a die attach film or the like, not illustrated.
- the semiconductor device 1 A is provided with a pad 11 a connected to the gate electrode 11 of the HEMT 10 , and a pad 12 a (for example, a source pad) and a pad 13 a (for example, a drain pad) connected to the electrode 12 and the electrode 13 described above that each function as a source electrode or a drain electrode.
- the pad 11 a , the pad 12 a, and the pad 13 a are respectively connected to a gate lead 211 , a source lead 212 , and a drain lead 213 of the lead frame 210 using wires 230 of aluminum or the like.
- the lead frame 210 , the semiconductor device 1 A mounted on the lead frame 210 , and the wires 230 used as connections are sealed by the resin 220 so as to expose parts of the gate lead 211 , the source lead 212 , and the drain lead 213 .
- the semiconductor package 200 with the configuration described above is obtained using the semiconductor device 1 A given in the first embodiment described above, for example.
- the cavity 31 a is provided so as to surround the gate electrode 11 , and by removing the insulating layer 32 with a relatively high permittivity via the opening 80 provided above the cavity 31 a , the parasitic capacitance is reduced, which suppresses deterioration in the characteristics, such as high frequency characteristics, due to parasitic capacitance.
- a high-performance semiconductor package 200 is realized.
- the semiconductor device 1 A is given here as one example, it is also possible to obtain a semiconductor package with the same high performance using the semiconductor device 1 B, 1 C, 1 D, 1 E, 1 F, or the like as described above in the second to fifth embodiments.
- a power factor correction circuit that uses a semiconductor device like those described above will now be described as a seventh embodiment.
- FIG. 20 depicts one example of a power factor correcting (PFC) circuit according to the seventh embodiment.
- FIG. 20 is an equivalent circuit diagram of one example of a PFC circuit according to the seventh embodiment.
- the PFC circuit 300 depicted in FIG. 20 includes a switch element 310 , a diode 320 , a choke coil 330 , a capacitor 340 , a capacitor 350 , a diode bridge 360 , and an alternating current (AC) power supply 370 .
- the drain electrode of the switch element 310 is connected to an anode terminal of the diode 320 and to one terminal of the choke coil 330 .
- the source electrode of the switch element 310 is connected to one terminal of the capacitor 340 and one terminal of the capacitor 350 .
- the other terminal of the capacitor 340 and the other terminal of the choke coil 330 are connected.
- the other terminal of the capacitor 350 and the cathode terminal of the diode 320 are connected.
- a gate driver is connected to the gate electrode of the switch element 310 .
- the AC power supply 370 is connected via the diode bridge 360 to both terminals of the capacitor 340 .
- a direct current (DC) power supply is connected to both terminals of the capacitor 350 .
- the semiconductor device 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, or the like as described above in the first to fifth embodiments is used as the switch element 310 of the PFC circuit 300 with the configuration described above.
- a cavity (the cavity 31 a or the cavity 113 a described above) is provided so as to surround a conductor (the gate electrode 11 , the wiring 111 , or the like described above) and an insulating layer (the insulating layer 32 or the insulating layer 114 described above) with a relatively high permittivity is removed by an opening (the opening 80 or the opening 120 described above) provided above the cavity.
- an opening the opening 80 or the opening 120 described above
- a power supply apparatus that uses a semiconductor device like those described above will now be described as an eighth embodiment.
- FIG. 21 depicts one example of a power supply apparatus according to the eighth embodiment.
- FIG. 21 is an equivalent circuit diagram of one example of a power supply apparatus according to the eighth embodiment.
- a power supply apparatus 400 depicted in FIG. 21 includes a primary side circuit 410 that is high-voltage, a secondary side circuit 420 that is low-voltage, and a transformer 430 provided between the primary side circuit 410 and the secondary side circuit 420 .
- the primary side circuit 410 includes a PFC circuit 300 like that described above in the seventh embodiment and an inverter circuit, such as a full-bridge inverter circuit 440 , connected between both terminals of the capacitor 350 of the PFC circuit 300 .
- the full-bridge inverter circuit 440 includes a plurality of (as one example here, four) switch elements, a switch element 441 , a switch element 442 , a switch element 443 , and a switch element 444 .
- the secondary side circuit 420 includes a plurality of (as one example here, three) switch elements, a switch element 421 , a switch element 422 , and a switch element 423 .
- the semiconductor device 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, or the like as described above in the first to fifth embodiments is used as the switch element 310 of the PFC circuit 300 included in the primary side circuit 410 and as the switch elements 441 to 444 of the full bridge inverter circuit 440 .
- Normal MIS (Metal Insulator Semiconductor)-type FET (Field Effect Transistors) that use silicon are used as the switch elements 421 to 423 of the secondary side circuit 420 of the power supply apparatus 400 .
- a cavity (the cavity 31 a or the cavity 113 a described above) is provided so as to surround a conductor (the gate electrode 11 , the wiring 111 , or the like described above) and an insulating layer (the insulating layer 32 or the insulating layer 114 described above) with a relatively high permittivity is removed by an opening (the opening 80 or the opening 120 described above) provided above the cavity.
- an opening the opening 80 or the opening 120 described above
- FIG. 22 depicts one example of an amplifier according to the ninth embodiment.
- FIG. 22 is an equivalent circuit diagram of one example of an amplifier according to the ninth embodiment.
- An amplifier 500 depicted in FIG. 22 includes a digital pre-distortion circuit 510 , a mixer 520 , a mixer 530 , and a power amplifier 540 .
- the digital pre-distortion circuit 510 compensates for nonlinear distortion in an input signal.
- the mixer 520 mixes the input signal SI, for which nonlinear distortion has been compensated, and an AC signal.
- the power amplifier 540 amplifies the signal produced by mixing the input signal SI and the AC signal.
- the amplifier 500 by switching switches for example, it is possible to mix an output signal SO and an AC signal at the mixer 530 and transmit the mixed signal to the digital pre-distortion circuit 510 .
- the amplifier 500 may be used as a high-frequency amplifier and a high-power amplifier.
- the semiconductor device 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, or the like as described above in the first to fifth embodiments is used as the power amplifier 540 .
- a cavity (the cavity 31 a or the cavity 113 a described above) is provided so as to surround a conductor (the gate electrode 11 , the wiring 111 , or the like described above) and an insulating layer (the insulating layer 32 or the insulating layer 114 described above) with a relatively high permittivity is removed by an opening (the opening 80 or the opening 120 described above) provided above the cavity.
- an opening the opening 80 or the opening 120 described above
- Various electronic devices that use the semiconductor devices 1 A, 1 B, 1 C, 1 D, 1 E, 1 F and the like may be installed in various electronic appliances.
- a computer a personal computer, super computer, server, or the like
- a smartphone a mobile phone
- a tablet a sensor
- a camera a camera
- audio equipment a measuring apparatus
- a testing apparatus a manufacturing apparatus.
- a semiconductor device where the generation of parasitic capacitance due to an insulating layer is suppressed is realized.
- An electronic device equipped with this semiconductor device is also realized.
Abstract
Description
- This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2016-254877, filed on Dec. 28, 2016, the entire contents of which are incorporated herein by reference.
- The embodiments discussed herein are related to a semiconductor device, a method for manufacturing a semiconductor device, and an electronic device.
- Two known technologies for reducing the parasitic capacitance generated in a semiconductor device are a technology where the permittivity of an insulating layer that covers a gate electrode or wiring is reduced and a technology where an insulating layer that covers a gate electrode or wiring is provided with a cavity (space) surrounding the gate electrode or wiring.
- See, for example, the following documents.
- Japanese Laid-open Patent Publication No. 11-274175
- Japanese Laid-open Patent Publication No. 2009-272433
- Japanese Laid-open Patent Publication No. 2015-204365
- For a semiconductor device provided with an insulating layer that covers the gate electrode or wiring and has a cavity surrounding the gate electrode or wiring, when a further insulating layer is provided on top of the insulating layer, there is the risk of parasitic capacitance being generated due to this upper insulating layer, which would cause deterioration in the characteristics of the semiconductor device.
- According to one aspect, there is provided a semiconductor device including: a substrate; a first conductor provided on the substrate; a first insulating layer which is provided on the substrate, covers the first conductor, and has a cavity that surrounds the first conductor; and a second insulating layer which is provided on the first insulating layer and has an opening at a position corresponding to the cavity.
- The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
- It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention.
-
FIG. 1 depicts one example of a semiconductor device; -
FIG. 2 depicts a first example configuration of a semiconductor device according to a first embodiment; -
FIGS. 3A to 3C depict a cavity and an opening according to the first embodiment; -
FIG. 4 depicts a second example configuration of a semiconductor device according to the first embodiment; -
FIGS. 5A to 5C are first diagrams depicting a method for forming a semiconductor device according to a second embodiment; -
FIGS. 6A to 6C are second diagrams depicting a method for forming a semiconductor device according to the second embodiment; -
FIGS. 7A and 7B are third diagrams depicting a method for forming a semiconductor device according to the second embodiment; -
FIGS. 8A and 8B are fourth diagrams depicting a method for forming a semiconductor device according to the second embodiment; -
FIGS. 9A and 9B depict a first example configuration of a semiconductor device according to a third embodiment; -
FIGS. 10A and 10B depict a second example configuration of a semiconductor device according to the third embodiment; -
FIGS. 11A to 11C are first diagrams depicting an example of a method for forming a semiconductor device according to a fourth embodiment; -
FIGS. 12A and 12B are second diagrams depicting an example of a method for forming a semiconductor device according to the fourth embodiment; -
FIGS. 13A to 13C depict a different example of a method for forming a semiconductor device according to the fourth embodiment; -
FIGS. 14A to 14C depict a different example of a method for forming a semiconductor device according to the fourth embodiment; -
FIGS. 15A and 15B depict a different example of a method for forming a semiconductor device according to the fourth embodiment; -
FIGS. 16A and 16B depict one example of a semiconductor device according to a fifth embodiment; -
FIGS. 17A to 17C depict (a first part of) a method for forming a semiconductor device according to the fifth embodiment; -
FIGS. 18A to 18C depict (a second part of) a method for forming a semiconductor device according to the fifth embodiment; -
FIG. 19 depicts one example of a semiconductor package according to a sixth embodiment; -
FIG. 20 depicts one example of a power factor correcting circuit according to a seventh embodiment; -
FIG. 21 depicts one example of a power supply apparatus according to an eighth embodiment; and -
FIG. 22 depicts one example of an amplifier according to a ninth embodiment. - Several embodiments will be described below with reference to the accompanying drawings, wherein like reference numerals refer to like elements throughout.
-
FIG. 1 depicts one example of a semiconductor device.FIG. 1 schematically depicts a principal part of this example of a semiconductor device in cross section. - A
semiconductor device 600 depicted inFIG. 1 is equipped with a high electron mobility transistor (HEMT) 610. - A
compound semiconductor layer 620 including a channel layer (electron transit layer), a spacer layer, an electron supply layer, a cap layer, and the like is used in thesemiconductor device 600. - A
gate electrode 611 of the HEMT 610 is provided together with a pair ofelectrodes element isolation region 621 of thecompound semiconductor layer 620. Theelectrode 612 is used as a source electrode or a drain electrode of theHEMT 610 and is connected to (the electron supply layer of) thecompound semiconductor layer 620. Theelectrode 613 is used as the drain electrode or the source electrode of theHEMT 610 and is connected to (the electron supply layer of) thecompound semiconductor layer 620. Aninsulating layer 630 is formed using silicon nitride (SiN), silicon oxide (SiO2), or the like in the active region, and thegate electrode 611 passes through theinsulating layer 630 and is connected to (the cap layer of) thecompound semiconductor layer 620. InFIG. 1 , thegate electrode 611 whose cross-sectional form is T-shaped is illustrated. - The HEMT 610 is covered with an
insulating layer 631 that uses a material with a relatively low permittivity, such as a so-called “Low-k material”. The insulatinglayer 631 has acavity 631 a that surrounds thegate electrode 611. In thesemiconductor device 600, an insulatinglayer 632, which uses a material with a relatively high permittivity such as SiN, is provided on the insulatinglayer 631, and an insulatinglayer 633, which uses a material with a relatively low permittivity such as a Low-k material, is further provided on the insulatinglayer 632. As one example, an insulatinglayer 634 which uses a material with a relatively high permittivity, such as SiN, is provided on the insulatinglayer 633. As the material with a relatively high permittivity used in the insulatinglayer 631 and the insulatinglayer 633, it is possible to use silsesquioxane. This material has a cage-like molecular structure, so that holes due to the molecular structure are formed inside the insulatinglayer 631 and the insulatinglayer 633 formed using silsesquioxane. That is, the insulatinglayer 631 and the insulatinglayer 633 are porous layers. -
Contacts layer 634, the insulatinglayer 633, the insulatinglayer 632, the insulatinglayer 631, and the insulatinglayer 630. Wiring 650 a that is connected to thecontact 640 a and thecontact 640 c andwiring 650 b that is connected to thecontact 640 b are provided on the insulatinglayer 634. Thecontact 640 a and thewiring 650 a are connected to theelectrode 612 of theHEMT 610 and thecontact 640 b and thewiring 650 b are connected to theelectrode 613 of theHEMT 610. Thecontact 640 c, which is joined to theelectrode 612 of theHEMT 610 via thewiring 650 a and thecontact 640 a, is connected for example to conductors (not illustrated), such as vias and backside electrodes provided on thecompound semiconductor layer 620. - In addition, a passive element, for example, a
capacitor 660, is mounted together with theHEMT 610 on thecompound semiconductor layer 620 of thesemiconductor device 600. In thesemiconductor device 600, acapacitor 660, which is configured by sandwiching a part of the insulatinglayer 632 that has a relatively high permittivity between alower electrode 661 and anupper electrode 662, is provided on thecompound semiconductor layer 620. - HEMI have superior high-speed characteristics and are used in the signal processing circuits of optical communication systems and other high-speed digital circuits. In particular, since HEMI have excellent low-noise characteristics, they are expected to be utilized in amplifiers for microwave and millimeter wave bands. When operating an amplifier in the millimeter wave bands, a high current gain cutoff frequency (fT) is demanded to obtain a sufficient amplification gain. For this reason, in addition to improving the transconductance (gm), which is a parameter related to the amplification factor of a transistor, it is important to shorten the gate length to reduce the capacitance between the gate and the source. In addition, when a monolithic microwave integrated circuit (MMIC) is produced to reduce the module size, a parasitic capacitance is generated by the insulating layer between the wiring, which makes it important to reduce the permittivity of the insulating film. Accordingly, a material with a relatively low permittivity, such as benzocyclobutene or polysilazane, is used for the (insulating material of the) wiring layer of the MMIC. A technique for removing the insulation material to hollow out a cavity that surrounds a HEMI, where the influence on the high frequency characteristics is large, has been proposed.
- When, as in the
semiconductor device 600 depicted inFIG. 1 , acavity 631 a is provided in the insulatinglayer 631 covering theHEMI 610 at a part that surrounds thegate electrode 611, the parasitic capacitance generated between thegate electrode 611 and other conductors is reduced compared to a configuration where an insulating material (Low-k material, SiN, or the like) is provided at the same part. With thesemiconductor device 600, by reducing the parasitic capacitance by providing thecavity 631 a, deterioration in the characteristics of theHEMI 610, for example, the high-frequency characteristics where full use is made of the high speed of theHEMI 610, is suppressed. - However, in the
semiconductor device 600 with the configuration described above, to construct an MMIC, the insulatinglayer 632 and the insulatinglayer 633 for example are further provided on top of the insulatinglayer 631 that covers theHEMI 610 and has thecavity 631 awhich surrounds thegate electrode 611. Out of these layers, a material with a relatively low permittivity, such as a Low-k material, is used for the insulatinglayer 631 and the insulatinglayer 633, and a material with a relatively high permittivity, such as SiN, is used for the insulatinglayer 632. Due to the insulatinglayer 632 with a relatively high permittivity being provided on top of the insulatinglayer 631 with a relatively low permittivity, there is the possibility of parasitic capacitance being generated in thesemiconductor device 600 due to the insulatinglayer 632. There is the risk of this parasitic capacitance generated due to the insulatinglayer 632 causing deterioration in characteristics, such as the high-frequency characteristics, of thesemiconductor device 600. - The insulating
layer 632 that uses a material with a relatively high permittivity, such as SiN, may be used for example as a hard mask when etching the insulatinglayer 631 that uses a material with a relatively low permittivity, such as a Low-k material, and/or may be used as a dielectric of thecapacitor 660 in the MMIC. This means that it is difficult to produce anMMIC semiconductor device 600 with a configuration that does not include the insulatinglayer 632. - As one example, the following method is used to form the
cavity 631 a. First, a sacrificial layer (filler) that uses a material that decomposes under light, such as ultraviolet rays, is formed on the insulatinglayer 630 above thecompound semiconductor layer 620 in which theHEMT 610 is formed, so as to cover thegate electrode 611. The porousinsulating layer 631 is formed on this sacrificial layer. After this, irradiation with light, such as ultraviolet rays, is performed to cause decomposition and gasification of the sacrificial layer surrounding thegate electrode 611. The components of the gasified sacrificial layer are removed through the holes in the porous insulatinglayer 631. By removing the sacrificial layer, thecavity 631 a is formed so as to surround thegate electrode 611. - With a method that uses light to cause decomposition and gasification of a sacrificial layer to remove the sacrificial layer through the holes in the insulating
layer 631, to remove the sacrificial layer, it is needless to form holes that pass through the insulatinglayer 631 and reach the sacrificial layer. For this reason, holes that reach thecavity 631 a that surrounds thegate electrode 611 are not formed, which is effective from the viewpoint of achieving moisture resistance. - However, when the insulating
layer 632 is also formed using a material with a relatively high permittivity, such as SiN, on top of the insulatinglayer 631 as described above, there is a drop in the transmittance of light, such as ultraviolet rays, which may result in insufficient decomposition and gasification of the sacrificial layer. In addition, an insulatinglayer 632 formed using a material with a relatively high permittivity, such as SiN, is a denser film than the porous insulatinglayer 631 that has a relatively low permittivity. When a relatively denseinsulating layer 632 is present on the insulatinglayer 631 as described above, even when the sacrificial layer is caused to decompose and is gasified using light, it is difficult for the components of the gasified sacrificial layer to escape through the insulatinglayer 632, so that the sacrificial layer may be left around thegate electrode 611, preventing the parasitic capacitance from being sufficiently reduced. - In view of the problems described above, the configurations given in the following embodiments are used to realize semiconductor devices that each have a cavity that surrounds the gate electrode.
- First, a first embodiment will be described.
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FIG. 2 depicts a first example configuration of a semiconductor device according to the first embodiment.FIG. 2 schematically depicts a principal part of the first example configuration of a semiconductor device according to the first embodiment in cross section. - A
semiconductor device 1A depicted inFIG. 2 includes acompound semiconductor layer 20 and aHEMT 10 formed using thecompound semiconductor layer 20. - The
compound semiconductor layer 20 includes anelectron transit layer 20 c, aspacer layer 20 d, anelectron supply layer 20 e, and acap layer 20 f that are stacked on asemiconductor substrate 20 a, such as silicon carbide (SiC), with abuffer layer 20 b in between. - When the
HEMT 10 is configured as a GaN-type HEMT, where gallium nitrogen (GaN) and aluminum gallium nitrogen (AlGaN) are used as materials, the following structure is used for example as thecompound semiconductor layer 20. i-type GaN layers (i-GaN) are used for thebuffer layer 20 b and theelectron transit layer 20 c. An i-type AlGaN layer (i-AlGaN) is used for thespacer layer 20 d. An n-type AlGaN layer (n-AlGaN) is used for theelectron supply layer 20 e. An n-type GaN layer (n-GaN) is used for thecap layer 20 f. Due to piezoelectric polarization produced by the strain caused by the difference in lattice constants between GaN and AlGaN and spontaneous polarization of the AlGaN, two-dimensional electron gas (2 DEG) is formed in the vicinity of the upper surface of theelectron transit layer 20 c. - A
gate electrode 11 of theHEMT 10 and a pair ofelectrodes element isolation region 21 of thecompound semiconductor layer 20. Theelectrode 12 is used as a source electrode or a drain electrode of theHEMT 10, and theelectrode 13 is used as a drain electrode or a source electrode of theHEMT 10. Theelectrode 12 and theelectrode 13 are connected (ohmically connected) to theelectron supply layer 20 e of thecompound semiconductor layer 20. Both theelectrodes 12 and theelectrode 13 are made of metal materials, such as titanium (Ti) or aluminum (Al). - An insulating
layer 30 is formed using SiN or the like in the active region. Thecap layer 20 f of thecompound semiconductor layer 20, and theelectrode 12 and theelectrode 13 are covered by the insulatinglayer 30. Thegate electrode 11 passes through the insulatinglayer 30 and is connected to thecap layer 20 f. InFIG. 2 , thegate electrode 11 whose cross-sectional form is T-shaped is illustrated. Metal materials, such as nickel (Ni) and gold (Au), are used for thegate electrode 11. - The
HEMT 10 is covered with an insulatinglayer 31 that uses a material with a relatively low permittivity, such as a Low-k material. The insulatinglayer 31 has acavity 31 a that surrounds thegate electrode 11. In thesemiconductor device 1A, the insulatinglayer 32 that uses a material with a relatively high permittivity, such as SiN, is provided on the insulatinglayer 31, and an insulatinglayer 33 that uses a material with a relatively low permittivity, such as a Low-k material, is further provided on the insulatinglayer 32. As one example, an insulatinglayer 34 that uses a material with a relatively high permittivity, such as SiN, is provided on the insulatinglayer 33. Silsesquioxane, for example, methyl silsesquioxane, is used as the material with a relatively low permittivity that is used for the insulatinglayer 31 and the insulatinglayer 33. This material has a cage-like molecular structure, so that holes due to the molecular structure are formed inside the insulatinglayer 31 and the insulatinglayer 33 that are formed using this material. That is, the insulatinglayer 31 and the insulatinglayer 33 are porous layers. - A
contact 40 a, acontact 40 b, and acontact 40 c are provided so as to pass through the insulatinglayer 34, the insulatinglayer 33, the insulatinglayer 32, the insulatinglayer 31, and the insulatinglayer 30.Wiring 50 a connected to thecontact 40 a and thecontact 40 c andwiring 50 b connected to thecontact 40 b are provided on the insulatinglayer 34. Also, although not depicted in the drawing, a contact that passes through the insulatinglayer 34, the insulatinglayer 33, the insulatinglayer 32, the insulatinglayer 31 and the insulatinglayer 30 and is connected to thegate electrode 11, and wiring connected to this contact are additionally provided. - The
contact 40 a and thewiring 50 a are connected to theelectrode 12 of theHEMT 10, and thecontact 40 b and thewiring 50 b are connected to theelectrode 13 of theHEMT 10. Thecontact 40 c, which is joined to theelectrode 12 of theHEMT 10 via thewiring 50 a and thecontact 40 a, is connected to conductors (not illustrated), such as vias and backside electrodes provided on thecompound semiconductor layer 20. Metal materials, such as titanium tungsten (TiW) and Au, are used for thecontact 40 a and thewiring 50 a, and also thecontact 40 b and thewiring 50 b. Similarly, metal materials are used for the other conductors, such as thecontact 40 c. - In addition, a passive element, such as a
capacitor 60, is provided together with theHEMT 10 on thecompound semiconductor layer 20 of thesemiconductor device 1A. In thesemiconductor device 1A, thecapacitor 60, which is configured by sandwiching a part of the insulatinglayer 32 that has a relatively high permittivity between alower electrode 61 and anupper electrode 62, is provided on thecompound semiconductor layer 20. - In the
semiconductor device 1A, above the insulatinglayer 31 that covers thegate electrode 11 of theHEMI 10 and has thecavity 31 a that surrounds thegate electrode 11, anopening 80 is provided at a position corresponding to thecavity 31 a of the insulatinglayer 31 so as to pass through the insulatinglayer 32, the insulatinglayer 33, and the insulatinglayer 34. - By being provided with the
opening 80, thesemiconductor device 1A is constructed so that the insulating layer 32 (and the insulating layer 34) that has a relatively high permittivity is partially removed from above (at least part of) thecavity 31 a of the insulatinglayer 31. With this configuration, the parasitic capacitance generated between thegate electrode 11 positioned inside thecavity 31 a and other conductors, for example, theelectrode 12, theelectrode 13, or thecontact 40 a or thecontact 40 b connected to theelectrodes semiconductor device 1A, thecavity 31 a is provided so as to surround thegate electrode 11 and the insulatinglayer 32, which has a relatively high permittivity, is removed by the opening 80 from above thecavity 31 a, so that the generation of parasitic capacitance is suppressed. By doing so, deterioration in the characteristics, such as the high-frequency characteristics, of thesemiconductor device 1A due to parasitic capacitance is suppressed. - In the
semiconductor device 1A, the part of the insulatinglayer 32 remaining after the part above thecavity 31 a has been removed may be used as a hard mask or may be used as the dielectric of thecapacitor 60. -
FIGS. 3A to 3C depict the cavity and the opening according to the first embodiment.FIGS. 3A to 3C schematically depict, when looking from the insulatinglayer 32 side, example planar layouts of principal parts of theHEMT 10 described above and the insulatinglayer 31 and the insulating layer 32 (and the insulatinglayers 33 and 34) provided on top of theHEMT 10. - For the
HEMT 10, theelectrodes gate electrode 11. Thecontact 40 d is connected to thegate electrode 11, and thecontact 40 a and thecontact 40 b are respectively connected to theelectrode 12 and theelectrode 13. Thecavity 31 a of the insulatinglayer 31 that covers thegate electrode 11 is provided so as to surround thegate electrode 11. As one example, a configuration where thecavity 31 a is provided in a region between theelectrode 12 and theelectrode 13 and encloses part of thegate electrode 11 is illustrated in the drawings. - The
opening 80 is provided in the insulatinglayer 32 above the insulatinglayer 31 at a position corresponding to thecavity 31 a of the insulatinglayer 31. As depicted inFIG. 3A for example, theopening 80 corresponding to thecavity 31 a may be formed in a size that is the same or similar to thecavity 31 a when looking from above. - Alternatively, as depicted in
FIG. 3B for example, theopening 80 provided corresponding to thecavity 31 a may be formed larger than thecavity 31 a when looking from above with a size that overlaps and encloses theentire cavity 31 a. Since it is possible, when anopening 80 of this size is provided, to increase the size of the region where the insulatinglayer 32 with a relatively high permittivity is not present above thecavity 31 a, it is possible to effectively reduce the parasitic capacitance caused by the insulatinglayer 32. When the size of theopening 80 is made larger than thecavity 31 a, it is possible to increase the efficiency of removal of the sacrificial layer when forming thecavity 31 a using a method, described later, that gasifies and removes the sacrificial layer by photodecomposition. - As yet another alternative, as depicted in
FIG. 3C for example, theopening 80 provided corresponding to thecavity 31 a may be produced in a size that is smaller than thecavity 31 a and overlaps part of thecavity 31 a when looking from above. Since it is possible, even when anopening 80 of this size is provided, to provide a region where the insulatinglayer 32 with a relatively high permittivity is not present above thecavity 31 a, it is possible to reduce the parasitic capacitance due to the insulatinglayer 32. However, it should be noted that when the size of theopening 80 is smaller than thecavity 31 a, depending on the size of theopening 80, the removal efficiency of the sacrificial layer may fall when forming thecavity 31 a using a method that gasifies and removes a sacrificial layer by photodecomposition as described later. - Note that although the
cavity 31 a that is a region between theelectrode 12 and theelectrode 13 and incorporates part of thegate electrode 11 is given here as an example, the region where thecavity 31 a is disposed (or “disposed region”) is not limited to this. As examples, thecavity 31 a may be provided so as to extend outside theelectrode 12 and theelectrode 13, and may be provided so as to incorporate theentire gate electrode 11. It is possible to provide theopening 80 corresponding to thecavity 31 a in keeping with the examples inFIGS. 3A to 3A based on the disposed region of thecavity 31 a and with consideration to the layout of thecontacts 40 a to 40 d and the like and the layout of thewiring FIGS. 3A to 3C ) connected to thecontacts 40 a to 40 d and the like. -
FIG. 4 depicts a second example configuration of a semiconductor device according to the first embodiment.FIG. 4 schematically depicts a principal part of the second example configuration of the semiconductor device according to the first embodiment in cross section. - A
semiconductor device 1B depicted inFIG. 4 differs from thesemiconductor device 1A described above by having a configuration where theopening 80 provided corresponding to thecavity 31 a is filled with an insulatinglayer 35. - As one example, a material, such as a Low-k material, with a relatively low permittivity that is lower than the material, such as SiN, used for the insulating
layer 32 is used as the insulatinglayer 35 that fills theopening 80. As this material, silsesquioxane, such as methyl silsesquioxane may be used. In this case, holes due to the cage-like molecular structure of the material are formed inside of the insulatinglayer 35 to be formed. That is, the insulatinglayer 35 is a porous layer. By using this material for the insulatinglayer 35, generation of parasitic capacitance due to the insulating portion provided above thecavity 31 a is suppressed. In addition, by filling theopening 80 with the insulatinglayer 35, resistance to moisture is increased, so that penetration of moisture into thecavity 31 a and theHEMT 10 and deterioration in the characteristics of theHEMT 10 due to moisture are suppressed. - When a material with relatively high transmittance of light, such as ultraviolet rays, and a relatively low density, such as a porous layer, is used as the insulating
layer 35 that fills theopening 80, it is possible, after theopening 80 has been filled with the insulatinglayer 35, to form thecavity 31 a using a method that gasifies and removes the sacrificial layer by photodecomposition as described later. - The insulating
layer 35 that fills theopening 80 may have a single-layer structure but may alternatively have a laminated structure where one or two or more insulating layers with a relatively low permittivity are laminated. Also, the insulatinglayer 35 that fills theopening 80 may have a laminated structure provided with one or two or more insulating layers with a relatively low permittivity on the lower side and with one or two or more insulating layers with a relatively high permittivity on the upper side. Even when a layer with a relatively high permittivity is provided on the upper side, so long as this is distant from thegate electrode 11, generation of parasitic capacitance due to this layer with a relatively high permittivity is suppressed. - It should be noted that the
HEMT 10 in thesemiconductor device 1A and thesemiconductor device 1B described above is not limited to the GaN-based HEMT described earlier which uses GaN and AlGaN as materials, and it is possible to configure a HEMT using other materials. - As examples, as the
HEMT 10, it is possible to configure a GaN-type HEMI that uses GaN and indium aluminum nitride (InAlN) as materials or a GaN-type HEMI that uses GaN and indium aluminum gallium nitrogen (InAlGaN) as materials. For a GaN-type HEMI that uses GaN and InAlN, i-GaN is used for theelectron transit layer 20 c of thecompound semiconductor layer 20, i-InAlN for thespacer layer 20 d, n-InAlN for theelectron supply layer 20 e, and n-GaN is used as thecap layer 20 f. For a GaN-type HEMI that uses GaN and InAlGaN, i-GaN is used for theelectron transit layer 20 c of thecompound semiconductor layer 20, i-InAlGaN is used for thespacer layer 20 d, n-InAlGaN is used for theelectron supply layer 20 e, and n-GaN is used for thecap layer 20 f. - In addition, as the
HEMI 10, aside from the various GaN-type HEMI described above, it is possible to configure an indium phosphorus (InP) type HEMI or the like. - Next, a second embodiment will be described.
- Here, the second embodiment is described as an example of a method for forming the
semiconductor device 1A and thesemiconductor device 1B described in the first embodiment. -
FIGS. 5A to 8B depict a method for forming a semiconductor device according to the second embodiment.FIGS. 5A to 5C ,FIGS. 6A to 6C ,FIGS. 7A and 7B , andFIGS. 8A and 8B schematically depict a principal part at each step in the method for forming a semiconductor device according to the second embodiment in cross section. - First, as depicted in
FIG. 5A , the compound semiconductor layer 20 (substrate) on which theHEMI 10 and the like have been formed is prepared. - For a GaN-type HEMI that uses GaN and AlGaN, first a
buffer layer 20 b and anelectron transit layer 20 c of i-GaN, aspacer layer 20 d of i-AlGaN, anelectron supply layer 20 e of n-AlGaN, and acap layer 20 f of n-GaN are laminated in that order on asemiconductor substrate 20 a of SiC or the like by MOVPE (Metal Organic Vapor Phase Epitaxy) for example to form thecompound semiconductor layer 20. - After this, the
element isolation region 21 is formed by ion implantation of argon (Ar), for example. - Next, the
electrode 12 and theelectrode 13 that are respectively used as a source electrode or a drain electrode are formed on theelectron supply layer 20 e. - At this time, first, a resist with an opening in a region where the
electrode 12 and theelectrode 13 are to be formed is formed on thecap layer 20 f of thecompound semiconductor layer 20 using a photolithography technique. By dry etching, for example dry etching using a chlorine-based gas, with the resist as a mask, thecap layer 20 f exposed to the opening in the resist is removed. After this, the metal material that forms theelectrode 12 and theelectrode 13, for example a Ti film and an Al film, is laminated and deposited on the entire surface, that is, on the upper surface of the resist and in the opening, and the Ti film and the Al film deposited on the upper surface of the resist are removed together with the resist (this method is called “lift-off”). By doing so, a Ti film and an Al film are formed on regions of theelectron supply layer 20 e of thecompound semiconductor layer 20 where theelectrode 12 and theelectrode 13 are to be formed. Next, a heat treatment, for example a heat treatment in a nitrogen atmosphere at a temperature of 400 to 1000° C., is performed. By performing this heat treatment, theelectrode 12 and theelectrode 13 that are ohmically connected to theelectron supply layer 20 e are formed. - Next, an insulating layer 30 (protective layer) that covers the
cap layer 20 f, theelectrode 12, and theelectrode 13 is formed on thecompound semiconductor layer 20. As one example, as the insulatinglayer 30, an SiN layer is formed by a CVD (Chemical Vapor Deposition) method. - After this, the
gate electrode 11 that passes through the insulatinglayer 30 and is connected to thecap layer 20 f is formed. - At this time, first, a resist with an opening in a region where the gate electrode 11 (for example, the leg portion of the T-shaped gate electrode 11) is to be formed is formed on the insulating
layer 30 using a photolithography technique. The insulatinglayer 30 exposed to the opening of the resist is removed by dry etching, for example dry etching using sulfur hexafluoride (SF6) gas, with the resist as a mask. After this, the resist is removed and a resist with an opening in a region that includes the region where thegate electrode 11 is to be formed is newly formed. Next, a metal material that forms thegate electrode 11, for example an Ni film and an Au film, is laminated and deposited on the entire surface, that is, on the upper surface of the newly formed resist and inside the opening, and after this, the resist is removed together with the Ni film and Au film deposited on the upper surface (this method is called “lift-off”). By doing so, a T-shapedgate electrode 11 is formed on thecap layer 20 f of thecompound semiconductor layer 20. - As one example, as depicted in
FIG. 5A , by using this method, thecompound semiconductor layer 20 on which theHEMI 10 and the like have been formed is obtained. - As depicted in
FIG. 5B , asacrificial layer 90 is formed on thecompound semiconductor layer 20 on which theHEMI 10 and the like have been formed. - As the
sacrificial layer 90, a material that decomposes under light, such as ultraviolet rays, is used. As one example, an organic layer that includes a functional group containing oxygen (carbonyl group (CO), carboxyl group (COOH), hydroxyl (OH), or the like) and is decomposed by ultraviolet rays with a wavelength of 300 to 400 nm is used as thesacrificial layer 90. In addition to methyl glutarimide, polymethyl methacrylate, polypropylene, and polycarbonate may be given as examples of this type of organic layer. - The material described above is formed by spin coating, for example, on the compound semiconductor layer on which the
HEMT 10 has been formed to form thesacrificial layer 90. The formedsacrificial layer 90 is patterned using a photolithography technique and an etching technique so as to remain in a predetermined region (or “disposed region”). As one example, thesacrificial layer 90 is patterned so as to remain in a region which, when viewed from above, is located between theelectrode 12 and theelectrode 13 and incorporates part or all of thegate electrode 11. Alternatively, thesacrificial layer 90 is patterned so as to remain in a region which, when viewed from above, incorporates part or all of thegate electrode 11 and also incorporates part or all of theelectrode 12 and part or all of theelectrode 13. - After formation of the
sacrificial layer 90, as depicted inFIG. 5C , the insulatinglayer 31, the insulatinglayer 32, the insulatinglayer 33, and the insulatinglayer 34 are formed. - When doing so, first the insulating
layer 31 is formed using a material with a relatively low permittivity so as to cover thesacrificial layer 90. As one example, a porous layer is formed as the insulatinglayer 31. - After this, the insulating
layer 32 is formed using a material with a relatively high permittivity on the formed insulatinglayer 31. As one example, an SiN layer is formed as the insulatinglayer 32. Although omitted from the drawings, the insulatinglayer 32 is used as the dielectric of thecapacitor 60 provided on thecompound semiconductor layer 20. Note that in this case, thelower electrode 61 is formed in advance in a region where thecapacitor 60 is to be formed before formation of the insulatinglayer 32, and after formation of the insulatinglayer 32, theupper electrode 62 that faces thelower electrode 61 with the insulatinglayer 32 in between is formed, thereby forming thecapacitor 60. - Next, the insulating
layer 33 is formed using a material with a relatively high permittivity on the formed insulatinglayer 32. As one example, a porous layer is formed as the insulatinglayer 33. The insulatinglayer 34 is then formed, using a material with a relatively high permittivity for example, on the formed insulatinglayer 33. As one example, an SiN layer is formed as the insulatinglayer 34. - After formation of the insulating
layer 31, the insulatinglayer 32, the insulatinglayer 33, and the insulatinglayer 34, as depicted inFIG. 6A , acontact hole 41 a and acontact hole 41 b that respectively reach theelectrode 12 and theelectrode 13 are formed. Here, although omitted from the drawings, a contact hole that reaches thegate electrode 11 is also formed together with thecontact hole 41 a and thecontact hole 41 b. - After formation of the
contact hole 41 a, thecontact hole 41 b, and the like, as depicted inFIG. 6B , thecontact 40 a, thecontact 40 b, and the like, and conductors such as thewiring 50 a, thewiring 50 b that are connected to thecontacts - At this time, first a metal material, for example a TiW film and an Au film, that forms the seed layer for plating, described later, is formed by sputtering on the entire surface, that is, on the upper surface of the insulating
layer 34 and the inner surfaces of thecontact hole 41 a and thecontact hole 41 b. After this, a resist with openings in regions where thewiring 50 a, thewiring 50 b, and the like are to be formed is formed on the seed layer, and a wiring metal material, for example an Au film, that forms thewiring FIG. 6B , thecontact 40 a that is connected to theelectrode 12, thewiring 50 a connected to thecontact 40 a, thecontact 40 b that is connected to theelectrode 13, and thewiring 50 b connected to thecontact 40 b are formed. In addition, although omitted from the drawings, the contact connected to thegate electrode 11 and the wiring connected to this contact are formed. - After formation of the
contact 40 a, thecontact 40 b, and the like, and formation of thewiring 50 a, thewiring 50 b, and the like, theopening 80 that passes through the insulatinglayer 34, the insulatinglayer 33, and the insulatinglayer 32 is formed as depicted inFIG. 6C . - The insulating
layer 34, the insulatinglayer 33, and the insulatinglayer 32 are removed in a region corresponding to thesacrificial layer 90 formed by patterning so as to keep the predetermined disposed region mentioned above, that is, a region that overlaps all or part of thesacrificial layer 90 when looking from above, thereby forming theopening 80. The insulatinglayer 34, the insulatinglayer 33, and the insulatinglayer 32 are removed using a photolithography technique and an etching technique. As one example, a resist with an opening in a predetermined region is formed, the insulatinglayer 34 is removed by etching using the resist as a mask, and the insulatinglayer 33 and the insulatinglayer 32 are then removed in that order. The etching conditions (etching gas, etching time, and the like) of the insulatinglayer 34, the insulatinglayer 33, and the insulatinglayer 32 are set based on the materials used for each layer, the thicknesses, and the like. - After formation of the
opening 80, as depicted inFIG. 7A , thesacrificial layer 90 under the insulatinglayer 31 is removed to form thecavity 31 a. - When doing so, as one example, light, such as ultraviolet rays that pass through the insulating
layer 31, is irradiated onto thesacrificial layer 90 through the insulatinglayer 31 in a vacuum. Thesacrificial layer 90 decomposes due to the incident light and is gasified. The components of the gasifiedsacrificial layer 90 are discharged to outside the insulatinglayer 31 through the holes in the porous insulatinglayer 31. By doing so, thecavity 31 a is formed in the insulatinglayer 31. - Here, due to the
opening 80 formed on the insulatinglayer 31 above thesacrificial layer 90, a structure is produced where the insulatinglayer 32, the insulatinglayer 33, and the insulatinglayer 34 have been partially removed. - Out of the insulating
layer 32, the insulatinglayer 33, and the insulatinglayer 34, the insulatinglayer 32 and the insulatinglayer 34 that use SiN or the like have a property of relatively low transmittance for light such as ultraviolet rays. Since the insulatinglayer 32, the insulatinglayer 33, and the insulatinglayer 34 present on the insulatinglayer 31, which include the insulatinglayer 32 and the insulatinglayer 34 with the property described above, are removed from above thesacrificial layer 90, it becomes easier for light such as ultraviolet rays to reach thesacrificial layer 90, which improves the efficiency of decomposition and gasification of thesacrificial layer 90. - In addition, the insulating
layer 32 and the insulatinglayer 34 that use SiN or the like have a further property of being relatively dense films. Since the insulatinglayer 32, the insulatinglayer 33, and the insulatinglayer 34 on the insulatinglayer 31, which include the insulatinglayer 32 and the insulatinglayer 34 with this further property, are removed from above thesacrificial layer 90, it becomes easier for the gasifiedsacrificial layer 90 to be discharged to outside the insulatinglayer 31, which improves the efficiency of removal of thesacrificial layer 90. - By forming the
opening 80 above thesacrificial layer 90, it is possible to form astable cavity 31 a where thesacrificial layer 90 does not remain under the insulatinglayer 31, that is, where thesacrificial layer 90 is prevented from remaining as residue around thegate electrode 11. - By performing the steps that have been described above with reference to
FIGS. 5A to 5C ,FIGS. 6A to 6C , andFIG. 7A , thesemiconductor device 1A described above (seeFIG. 2 ) is obtained. - With the
semiconductor device 1A, since the insulatinglayer 32 and the insulatinglayer 34 of SiN or the like that have a relatively high permittivity are removed from above thecavity 31 a and thesacrificial layer 90 is prevented from remaining as residue around thegate electrode 11 in thecavity 31 a, generation of parasitic capacitance caused by these layers is suppressed. By doing so, thesemiconductor device 1A, for which deterioration in the characteristics due to parasitic capacitance is suppressed, is realized. - When formation of the
cavity 31 a (i.e., removal of the sacrificial layer 90) as depicted inFIG. 7A is followed by filling theopening 80 above thecavity 31 a with the insulatinglayer 35 as depicted inFIG. 7B , thesemiconductor device 1B (seeFIG. 4 ) is obtained. As one example, after the formation of thecavity 31 a, theopening 80 is filled by spin coating or the like with a material that has a lower permittivity than the material, such as SiN, used for the insulatinglayer 32. - With the
semiconductor device 1B, by filling theopening 80 with the insulatinglayer 35, the resistance to moisture is improved. By doing so, thesemiconductor device 1B, in which penetration of moisture into thecavity 31 a and theHEMI 10 and resulting deterioration in the characteristics of theHEMI 10 are suppressed, is realized. - When forming the
semiconductor device 1B, the step of filling theopening 80 with the insulatinglayer 35 is not limited to being performed after formation of thecavity 31 a and may be performed before the formation of thecavity 31 a. - That is, after formation of the
opening 80 depicted inFIG. 6C , theopening 80 is filled with the insulatinglayer 35 as depicted inFIG. 8A without removing thesacrificial layer 90. After this, as depicted inFIG. 8B , thesacrificial layer 90 is removed to form thecavity 31 a. For the insulatinglayer 35, a porous material with a relatively high transmittance of light such as ultraviolet rays and a relatively low density is used. When this type of insulatinglayer 35 is used, even when theopening 80 is filled with the insulatinglayer 35 before the formation of thecavity 31 a (i.e., before removal of the sacrificial layer 90), light will still reach thesacrificial layer 90 to cause decomposition and gasification, and the gasified components are discharged through the holes in the insulatinglayer 31 and the insulatinglayer 35. When a material with higher porosity than the insulatinglayer 31 is used for the insulatinglayer 35, it is possible to increase the efficiency of removal of thesacrificial layer 90 compared to a case where a material with low porosity is used. - Note that when forming the
semiconductor device 1A and thesemiconductor device 1B, a step (called “back grinding”) of grinding the back surface of thecompound semiconductor layer 20 may be performed. Other processes may also be performed, such as formation of vias that pass through thecompound semiconductor layer 20 after grinding and are connected to conductors (for example, thecontact 40 c) on the wiring layer side and formation of electrodes on the back surface of thecompound semiconductor layer 20 after grinding. When the back grinding of thecompound semiconductor layer 20 is performed in this way, formation of thecavity 31 a (seeFIG. 7A or 8B ) or both formation of the opening 80 (seeFIG. 6C ) and formation of thecavity 31 a (seeFIG. 7A orFIG. 8B ) may be performed after the back grinding. Since a comparatively large force and/or high heat may act upon thecompound semiconductor layer 20 when back grinding is performed, when thecavity 31 a is already formed at this time, there is the risk of layers near thecavity 31 a peeling off due to the force and/or heat. On the other hand, when thecavity 31 a is yet to be formed, that is, when thesacrificial layer 90 is present, it is possible to effectively suppress the peeling of layers in the vicinity of thecavity 31 a when back grinding is performed. - Next, a third embodiment will be described.
- Here, a modification to the
semiconductor device 1A and thesemiconductor device 1B described above in the first and second embodiments will be described as a third embodiment. -
FIGS. 9A and 9B depict a first example configuration of a semiconductor device according to the third embodiment.FIG. 9A schematically depicts a principal part of the first example configuration of the semiconductor device according to the third embodiment in cross section.FIG. 9B schematically depicts the planar layout of a principal part of the first example configuration of the semiconductor device according to the third embodiment. Note thatFIG. 9A is a schematic cross-sectional view corresponding to the position of a line L9-L9 inFIG. 9B . - In the semiconductor device 1C depicted in
FIG. 9A , thecavity 31 a provided in the insulatinglayer 31 that covers thegate electrode 11 is formed so as to extend to the positions of (thecontact 40 a and thecontact 40 b connected to) theelectrode 12 and theelectrode 13 respectively used as a source electrode and a drain electrode. Theopening 80 is provided in the insulating layer 32 (and the insulatinglayer 33 and the insulating layer 34) on the insulatinglayer 31 corresponding to thiscavity 31 a. The semiconductor device 1C differs from thesemiconductor device 1A described above in this respect. - As depicted in
FIG. 9B for example, when looking from above, theopening 80 provided corresponding to thecavity 31 a is provided above thecavity 31 a while avoiding thewiring 50 a and thewiring 50 b connected to thecontact 40 a and thecontact 40 b. By widening thecavity 31 a and widening theopening 80 that is provided corresponding to thecavity 31 a, the insulatinglayer 32 with a relatively high permittivity that remains above theHEMT 10 is reduced, which reduces the parasitic capacitance caused by the insulatinglayer 32. By doing so, a semiconductor device 1C where deterioration in the characteristics due to parasitic capacitance is suppressed is realized. -
FIGS. 10A and 10B depict a second example configuration of a semiconductor device according to the third embodiment.FIG. 10A schematically depicts a principal part of the second example configuration of the semiconductor device according to the third embodiment in cross section.FIG. 10B schematically depicts the planar layout of a principal part of the second example configuration of the semiconductor device according to the third embodiment. Note thatFIG. 10A is a schematic cross-sectional view corresponding to the position of a line L10-L10 inFIG. 10B . - In a
semiconductor device 1D depicted inFIG. 10A , thecavity 31 a provided in the insulatinglayer 31 that covers thegate electrode 11 is formed so as to extend to positions outside (thecontact 40 a and thecontact 40 b connected to) theelectrode 12 and theelectrode 13 respectively used as the source electrode or the drain electrode. Theopening 80 is provided in the insulating layer 32 (and the insulatinglayer 33 and the insulating layer 34) on the insulatinglayer 31 corresponding to thiscavity 31 a. Thesemiconductor device 1D differs from thesemiconductor device 1A described above in this respect. - As depicted in
FIG. 10B for example, when looking from above, theopening 80 provided corresponding to thecavity 31 a is provided above thecavity 31 a while avoiding thewiring 50 a and thewiring 50 b connected to thecontact 40 a and thecontact 40 b. By widening thecavity 31 a and widening theopening 80 that is provided corresponding to thecavity 31 a, the insulatinglayer 32 with a relatively high permittivity that remains above theHEMI 10 is reduced, which reduces the parasitic capacitance caused by the insulatinglayer 32. By doing so, asemiconductor device 1D where deterioration in the characteristics due to parasitic capacitance is suppressed is realized. - Note that the planar forms of the
openings 80 in the semiconductor device 1C and thesemiconductor device 1D are not limited to the examples described above. It is possible to set the planar form of theopening 80 based on the layout of thecavity 31 a, as well as thecontact 40 a and thecontact 40 b and thewiring 50 a and thewiring 50 b connected to thecontacts - Also, in keeping with the example of the
semiconductor device 1B described above, theopenings 80 in the semiconductor device 1C and thesemiconductor device 1D may be filled with the insulatinglayer 35 which uses a material with a lower permittivity than the material, such as SiN, used for the insulatinglayer 32. - It is possible to form the semiconductor device 1C and the
semiconductor device 1D by appropriately changing the disposed region of the sacrificial layer 90 (seeFIG. 5B ) and the disposed region of the opening 80 (seeFIG. 6C ) in accordance with the example method for forming described in the second embodiment. - Next, a fourth embodiment will be described.
- Here, a number of alternative examples of methods of forming a semiconductor device will be described as the fourth embodiment.
-
FIGS. 11A to 11C andFIGS. 12A and 12B depict an example of a method for forming a semiconductor device according to the fourth embodiment.FIGS. 11A to 11C andFIGS. 12A and 12B schematically depict a principal part in each step in the method for forming a semiconductor device according to the fourth embodiment in cross section. - In this example, after the steps in
FIGS. 5A to 5C described in the second embodiment given above, as depicted inFIG. 11A , anopening 80 that passes through the insulatinglayer 34, the insulatinglayer 33, and the insulatinglayer 32 is formed. Theopening 80 is formed in a predetermined region by using a photolithography technique and an etching technique according to the example steps depicted inFIG. 6C described above. - After formation of the
opening 80, as depicted inFIG. 11B , thesacrificial layer 90 below the insulatinglayer 31 is removed to form thecavity 31 a. Thecavity 31 a is formed in accordance with the example steps inFIG. 7A described above by decomposing and gasifying thesacrificial layer 90 via irradiation with light, such as ultraviolet rays, and discharging the components of the gasifiedsacrificial layer 90 to outside the insulatinglayer 31 through the holes in the porous insulatinglayer 31. - After formation of the
cavity 31 a, as depicted inFIG. 11C , theopening 80 is filled with the insulatinglayer 35 that uses a material with a lower permittivity than the material, such as SiN, used for the insulatinglayer 32. - Note that in accordance with the example depicted in
FIGS. 8A and 8B described above, after theopening 80 has been filled with the insulatinglayer 35 following the formation of theopening 80, thesacrificial layer 90 may be removed through the holes in the insulatinglayer 31 and the insulatinglayer 35 to form thecavity 31 a. - After formation of the
cavity 31 a and the insulatinglayer 35, as depicted inFIG. 12A , thecontact 40 a, thecontact 40 b, and the like and thewiring 50 a, thewiring 50 b and the like connected to thecontacts FIGS. 6A and 6B described above. - The
semiconductor device 1B may be obtained using this method. - In a method that forms the
wiring 50 a, thewiring 50 b, and the like after forming thecavity 31 a and the insulatinglayer 35 that fills theopening 80 in this way, like thesemiconductor device 1B depicted inFIG. 12B , it is possible to form wiring 50 c on the insulatinglayer 35 that fills theopening 80. Thewiring 50 c may be formed separate from thewiring 50 a, thewiring 50 b, and the like. Alternatively, thewiring 50 c may be connected to or integrally formed with one of thewiring 50 a, thewiring 50 b, and the like. Since it is possible to also form thewiring 50 c on top of the insulatinglayer 35 that fills theopening 80, it is possible to increase the freedom with which the wiring is laid out in a semiconductor device 1Ba. - Note that when back grinding is performed on the
compound semiconductor layer 20, after back grinding, formation of thecavity 31 a or both formation of theopening 80 and formation of thecavity 31 a may be performed. In this way, when back grinding is performed in a state where thecavity 31 a is yet to be formed (i.e., where thesacrificial layer 90 is formed), it is possible to effectively suppress peeling of the layers near thecavity 31 a due to force and/or heat applied during back grinding. - The insulating layers provided on the
compound semiconductor layer 20 are not limited to the insulatinglayers 30 to 35 described above. As one example, it is possible to produce a structure formed using the method depicted inFIGS. 13A to 15B described below. -
FIGS. 13A to 15B depict different examples of methods of forming a semiconductor device according to the fourth embodiment.FIGS. 13A to 13C ,FIGS. 14A to 14C , andFIGS. 15A and 15B schematically depict a principal part at each step in other example methods of forming a semiconductor device according to the fourth embodiment in cross section. - In the method depicted in
FIGS. 13A to 13C , steps up to the formation of the insulatinglayer 34 are performed first and then as depicted inFIG. 13A , formation of an insulatinglayer 36 with a relatively low permittivity and an insulatinglayer 37 with a relatively high permittivity is performed. After this, as depicted inFIG. 13B , theopening 80 that passes through from the insulatinglayer 37 as far as the insulatinglayer 32 is formed, and by irradiating with light, such as ultraviolet rays, as depicted inFIG. 13C , thesacrificial layer 90 is removed through the porous insulatinglayer 31 to form thecavity 31 a. - In the method depicted in
FIGS. 14A to 14C , first after the steps up to formation of the insulatinglayer 35 have been performed without removing thesacrificial layer 90, as depicted inFIG. 14A , the insulatinglayer 36 that has a relatively low permittivity and the insulatinglayer 37 that has a relatively high permittivity are formed. After this, as depicted in FIG. 14B, anopening 82 that passes through the insulatinglayer 37 and the insulatinglayer 36 is formed, and theopening 82 is filled with a porous insulatinglayer 38 that has a relatively low permittivity (as one example, an insulatinglayer 38 whose porosity is equal to or higher than the insulatinglayer 31 and the insulating layer 35). After this, through irradiation with light such as ultraviolet rays, as depicted inFIG. 14C , thesacrificial layer 90 is removed through the porous insulatinglayer 31 and the insulatinglayer 38 to form thecavity 31 a. - In the method depicted in
FIGS. 15A and 15B , first, after formation of theopening 80, the structure depicted inFIG. 15A is obtained by removing thesacrificial layer 90 to form thecavity 31 a and then filling theopening 80 with the insulatinglayer 35, or alternatively by filling theopening 80 with the insulatinglayer 35 and then removing thesacrificial layer 90 to form thecavity 31 a. After this, as depicted inFIG. 15B , an insulatinglayer 39 with higher resistance to moisture than the insulatinglayer 35 is formed in a region that includes an area above the insulatinglayer 35 that fills theopening 80. By doing so, penetration of moisture into thecavity 31 a and theHEMI 10 and deterioration in the characteristics of theHEMI 10 due to moisture are suppressed. Note that although the insulatinglayer 39 with high resistance to moisture that is formed on the insulatinglayer 35 may have a higher permittivity than the insulatinglayer 31 and the insulatinglayer 35, since the insulatinglayer 39 is further from thegate electrode 11 than the insulatinglayer 32, it is possible to suppress the generation of parasitic capacitance due to the insulatinglayer 39. - It is possible to obtain a semiconductor device using methods like those depicted in
FIGS. 13A to 13C ,FIGS. 14A to 14C , andFIGS. 15A and 15B . When producing an MMIC semiconductor device, it is possible to make various changes to the composition and structure of the insulating layers provided on thecompound semiconductor layer 20, and by appropriately changing the steps in keeping with such changes, it is possible to provide theopening 80 and the like and thecavity 31 a. - Next, a fifth embodiment will be described.
- Although semiconductor devices provided with a cavity surrounding the gate electrode of a HEMI have been described above as examples, it is also possible to apply the methods described above to the wiring layers of a semiconductor device. An example of this is described below as a fifth embodiment.
-
FIGS. 16A and 16B depict one example of a semiconductor device according to the fifth embodiment.FIGS. 16A and 16B schematically depict a principal part of the semiconductor device according to the fifth embodiment in cross section. - A
semiconductor device 1E depicted inFIG. 16A and asemiconductor device 1F depicted inFIG. 16B are each equipped with asubstrate 100, which includes transistors (semiconductor elements) formed on a semiconductor substrate and one or two or more wiring layers, and awiring layer 110 provided on thesubstrate 100. - The
wiring layer 110 includeswiring 111 andwiring 112, an insulatinglayer 113 that covers thewiring 111 and thewiring 112, and an insulatinglayer 114 and an insulatinglayer 115 provided on top of the insulatinglayer 113. - The
wiring 111 and thewiring 112 may be wiring on which electrical signals of different potentials are supplied or may be wiring on which electrical signals of the same potential are supplied. - A material, such as a Low-k material, with a relatively low permittivity is used as the insulating
layer 113. As depicted inFIG. 16A for example, the insulatinglayer 113 has acavity 113 a that surrounds thewiring 111 and thewiring 112. Alternatively, as depicted inFIG. 16B for example, the insulatinglayer 113 includes thecavity 113 a that surrounds one out of thewiring 111 and the wiring 112 (in the illustrated example, the wiring 111). - The insulating
layer 114 that uses a material, such as SiN, with a relatively high permittivity, is provided on the insulatinglayer 113 and the insulatinglayer 115 that uses a material, such as a Low-k material, with a relatively low permittivity, is further provided on the insulatinglayer 114. - The
wiring layer 110 is provided with anopening 120 that passes through the insulatinglayer 114 and the insulatinglayer 115 above the insulatinglayer 113, which covers thewiring 111 and thewiring 112 and includes thecavity 113 a that surrounds one or both of thewiring 111 and thewiring 112, at a position corresponding to thecavity 113 a. - Note that although omitted from the drawing, contacts that are joined to other wiring are connected to the
wiring 111 and thewiring 112, for example by passing through the insulatinglayer 115, the insulatinglayer 114, and the insulatinglayer 113. - Since the
opening 120 is provided, thewiring layer 110 of thesemiconductor device 1E and thesemiconductor device 1F is constructed so that the insulatinglayer 114 that has a relatively high permittivity is partially removed from above (at least part of) thecavity 113 a of the insulatinglayer 113. By doing so, with thesemiconductor device 1E and thesemiconductor device 1F, the parasitic capacitance generated between thewiring 111 and thewiring 112 positioned inside thecavity 113 a or between thewiring 111 and other conductors is reduced, so that deterioration in the characteristics, such as the high frequency characteristics, is suppressed. -
FIGS. 17A to 17C andFIGS. 18A to 18C depict a method for forming a semiconductor device according to the fifth embodiment.FIGS. 17A to 17C andFIGS. 18A to 18C schematically depict a principal part at each step in the method for forming a semiconductor device according to the fifth embodiment in cross section. - First, as depicted in
FIG. 17A , thewiring 111 and thewiring 112 are formed on thesubstrate 100. - After formation of the
wiring 111 and thewiring 112, as depicted inFIG. 17B , asacrificial layer 130 is formed so as to cover thewiring 111 and thewiring 112. A material that decomposes due to light, such as ultraviolet rays, is used as thesacrificial layer 130. Thesacrificial layer 130 is formed in a predetermined region (or “disposed region”), for example a region that incorporates part or all of thewiring 111 and thewiring 112, using a photolithography technique and an etching technique. - After formation of the
sacrificial layer 130, as depicted inFIG. 17C , the insulatinglayer 113, the insulatinglayer 114, and the insulatinglayer 115 are formed. When doing so, the insulatinglayer 113 is formed using a material with a relatively high permittivity so as to cover thesacrificial layer 130, the insulatinglayer 114 is formed using a material with a relatively low permittivity on top of the insulatinglayer 113, and then the insulatinglayer 115 is formed using a material with a relatively low permittivity on the insulatinglayer 114. - After formation of the insulating
layer 113, the insulatinglayer 114, and the insulatinglayer 115, as depicted inFIG. 18A , theopening 120 that passes through the insulatinglayer 115 and the insulatinglayer 114 is formed. Theopening 120 is formed in a region corresponding to thesacrificial layer 130, that is, a region that entirely or partially overlaps thesacrificial layer 130 when looking from above. - After formation of the
opening 120, as depicted inFIG. 18B , thesacrificial layer 130 below the insulatinglayer 113 is removed to form thecavity 113 a. As one example, light, such as ultraviolet rays, that is transmitted by the insulatinglayer 113 is irradiated onto thesacrificial layer 130 through the insulatinglayer 113 and components of thesacrificial layer 130 produced by the resulting decomposition and gasification of thesacrificial layer 130 are discharged to the outside through the holes in the insulatinglayer 113 to form thecavity 113 a in the insulatinglayer 113. - By doing so, a
semiconductor device 1E like that depicted inFIG. 16A described above is obtained. By changing a disposed region of the sacrificial layer 130 (seeFIG. 17B ) and the formation region of the opening 120 (seeFIG. 18A ) corresponding to thesacrificial layer 130, asemiconductor device 1F like that depicted inFIG. 16B described above is obtained. - By forming the
opening 120 above thesacrificial layer 130 to partially remove the insulatinglayer 114 that has a relatively high permittivity, it is possible to sufficiently irradiate thesacrificial layer 130 with light, such as ultraviolet rays, and form astable cavity 113 a where thesacrificial layer 130 is prevented from remaining as residue under the insulatinglayer 113. By partially removing the insulatinglayer 114 with theopening 120 to ensure that thesacrificial layer 130 is removed, the generation of parasitic capacitance due to residue of thesacrificial layer 130 is suppressed, thereby realizing thesemiconductor device 1E and thesemiconductor device 1F where deterioration in the characteristics due to parasitic capacitance is suppressed. - As one example, after formation of the
cavity 113 a (seeFIG. 18B ), like a semiconductor device 1Ea depicted inFIG. 18C , theopening 120 may be filled with a porous insulatinglayer 116 which uses a material with a lower permittivity than the material used for the insulatinglayer 114. By doing so, resistance to moisture is improved, penetration of moisture into thecavity 113 a, deterioration in thewiring 111 and thewiring 112 due to moisture, and resulting deterioration in the characteristics of the semiconductor device 1Ea are suppressed. This also applies to thesemiconductor device 1F. Note that the step of filling theopening 120 with the insulatinglayer 116 may be performed after formation of the opening 120 (seeFIG. 18A ) but before formation of thecavity 113 a (seeFIG. 18B ). In this case, after formation of the opening 120 (seeFIG. 18A ), theopening 120 is filled with the porous insulatinglayer 116, and then thesacrificial layer 130 is removed through the insulatinglayer 113 and the insulatinglayer 116 to form thecavity 113 a. - When forming a
wiring layer 110 like that described above, it is possible to make the various changes described above in the second and fourth embodiments, such as changes to the order of steps when removing the sacrificial layer and/or forming the contacts). - Note that although the
semiconductor devices 1E, 1Ea, and 1F that include thewiring layer 110 have been described, it is also possible to use thewiring layer 110 with the configuration described above on a circuit board. - It is also possible to use the
semiconductor devices - First, a sixth embodiment will be described.
- Here, a semiconductor package that uses the semiconductor device like those described above will be described as the sixth embodiment.
-
FIG. 19 depicts one example of a semiconductor package according to the sixth embodiment.FIG. 19 schematically depicts a principal part of one semiconductor package according to the sixth embodiment in plan view. - A
semiconductor package 200 depicted inFIG. 19 includes alead frame 210 on which thesemiconductor device 1A described in the first embodiment, for example, is mounted, andresin 220 that seals thelead frame 210 and thesemiconductor device 1A. - The
semiconductor device 1A is mounted on diepads 210 a of thelead frame 210 using a die attach film or the like, not illustrated. Thesemiconductor device 1A is provided with apad 11 a connected to thegate electrode 11 of theHEMT 10, and apad 12 a (for example, a source pad) and apad 13 a (for example, a drain pad) connected to theelectrode 12 and theelectrode 13 described above that each function as a source electrode or a drain electrode. - The
pad 11 a, thepad 12 a, and thepad 13 a are respectively connected to agate lead 211, asource lead 212, and adrain lead 213 of thelead frame 210 usingwires 230 of aluminum or the like. Thelead frame 210, thesemiconductor device 1A mounted on thelead frame 210, and thewires 230 used as connections are sealed by theresin 220 so as to expose parts of thegate lead 211, thesource lead 212, and thedrain lead 213. - The
semiconductor package 200 with the configuration described above is obtained using thesemiconductor device 1A given in the first embodiment described above, for example. - In the
semiconductor device 1A, thecavity 31 a is provided so as to surround thegate electrode 11, and by removing the insulatinglayer 32 with a relatively high permittivity via theopening 80 provided above thecavity 31 a, the parasitic capacitance is reduced, which suppresses deterioration in the characteristics, such as high frequency characteristics, due to parasitic capacitance. By using a high-performance semiconductor device like this, a high-performance semiconductor package 200 is realized. - Although the
semiconductor device 1A is given here as one example, it is also possible to obtain a semiconductor package with the same high performance using thesemiconductor device - Next, a seventh embodiment will be described.
- A power factor correction circuit that uses a semiconductor device like those described above will now be described as a seventh embodiment.
-
FIG. 20 depicts one example of a power factor correcting (PFC) circuit according to the seventh embodiment.FIG. 20 is an equivalent circuit diagram of one example of a PFC circuit according to the seventh embodiment. - The
PFC circuit 300 depicted inFIG. 20 includes aswitch element 310, adiode 320, achoke coil 330, acapacitor 340, acapacitor 350, adiode bridge 360, and an alternating current (AC)power supply 370. - In the
PFC circuit 300, the drain electrode of theswitch element 310 is connected to an anode terminal of thediode 320 and to one terminal of thechoke coil 330. The source electrode of theswitch element 310 is connected to one terminal of thecapacitor 340 and one terminal of thecapacitor 350. The other terminal of thecapacitor 340 and the other terminal of thechoke coil 330 are connected. The other terminal of thecapacitor 350 and the cathode terminal of thediode 320 are connected. Also, a gate driver is connected to the gate electrode of theswitch element 310. TheAC power supply 370 is connected via thediode bridge 360 to both terminals of thecapacitor 340. A direct current (DC) power supply is connected to both terminals of thecapacitor 350. - The
semiconductor device switch element 310 of thePFC circuit 300 with the configuration described above. - In the
semiconductor device cavity 31 a or thecavity 113 a described above) is provided so as to surround a conductor (thegate electrode 11, thewiring 111, or the like described above) and an insulating layer (the insulatinglayer 32 or the insulatinglayer 114 described above) with a relatively high permittivity is removed by an opening (theopening 80 or theopening 120 described above) provided above the cavity. By doing so, the parasitic capacitance is reduced and deterioration in the characteristics, such as the high-frequency characteristics, due to parasitic capacitance is suppressed. By using a high-performance semiconductor device like this, a high-performance PFC circuit 300 is realized. - Next, an eighth embodiment will be described.
- A power supply apparatus that uses a semiconductor device like those described above will now be described as an eighth embodiment.
-
FIG. 21 depicts one example of a power supply apparatus according to the eighth embodiment.FIG. 21 is an equivalent circuit diagram of one example of a power supply apparatus according to the eighth embodiment. - A
power supply apparatus 400 depicted inFIG. 21 includes aprimary side circuit 410 that is high-voltage, asecondary side circuit 420 that is low-voltage, and atransformer 430 provided between theprimary side circuit 410 and thesecondary side circuit 420. - The
primary side circuit 410 includes aPFC circuit 300 like that described above in the seventh embodiment and an inverter circuit, such as a full-bridge inverter circuit 440, connected between both terminals of thecapacitor 350 of thePFC circuit 300. The full-bridge inverter circuit 440 includes a plurality of (as one example here, four) switch elements, aswitch element 441, aswitch element 442, aswitch element 443, and aswitch element 444. - The
secondary side circuit 420 includes a plurality of (as one example here, three) switch elements, aswitch element 421, aswitch element 422, and aswitch element 423. - In the
power supply apparatus 400 of this configuration, thesemiconductor device switch element 310 of thePFC circuit 300 included in theprimary side circuit 410 and as theswitch elements 441 to 444 of the fullbridge inverter circuit 440. Normal MIS (Metal Insulator Semiconductor)-type FET (Field Effect Transistors) that use silicon are used as theswitch elements 421 to 423 of thesecondary side circuit 420 of thepower supply apparatus 400. - In each
semiconductor device cavity 31 a or thecavity 113 a described above) is provided so as to surround a conductor (thegate electrode 11, thewiring 111, or the like described above) and an insulating layer (the insulatinglayer 32 or the insulatinglayer 114 described above) with a relatively high permittivity is removed by an opening (theopening 80 or theopening 120 described above) provided above the cavity. By doing so, the parasitic capacitance is reduced and deterioration in the characteristics, such as the high-frequency characteristics, due to parasitic capacitance is suppressed. By using a high-performance semiconductor device like this, a high-performancepower supply apparatus 400 is realized. - Next, a ninth embodiment will be described.
- An amplifier that uses a semiconductor device like those described above will now be described as a ninth embodiment.
-
FIG. 22 depicts one example of an amplifier according to the ninth embodiment.FIG. 22 is an equivalent circuit diagram of one example of an amplifier according to the ninth embodiment. - An
amplifier 500 depicted inFIG. 22 includes adigital pre-distortion circuit 510, amixer 520, amixer 530, and apower amplifier 540. - The
digital pre-distortion circuit 510 compensates for nonlinear distortion in an input signal. Themixer 520 mixes the input signal SI, for which nonlinear distortion has been compensated, and an AC signal. Thepower amplifier 540 amplifies the signal produced by mixing the input signal SI and the AC signal. In theamplifier 500, by switching switches for example, it is possible to mix an output signal SO and an AC signal at themixer 530 and transmit the mixed signal to thedigital pre-distortion circuit 510. Theamplifier 500 may be used as a high-frequency amplifier and a high-power amplifier. - In the
amplifier 500 of this configuration, thesemiconductor device power amplifier 540. - In the
semiconductor device cavity 31 a or thecavity 113 a described above) is provided so as to surround a conductor (thegate electrode 11, thewiring 111, or the like described above) and an insulating layer (the insulatinglayer 32 or the insulatinglayer 114 described above) with a relatively high permittivity is removed by an opening (theopening 80 or theopening 120 described above) provided above the cavity. By doing so, the parasitic capacitance is reduced and deterioration in the characteristics, such as the high-frequency characteristics, due to the parasitic capacitance is suppressed. By using a high-performance semiconductor device like this, a high-performance amplifier 500 is realized. - Various electronic devices that use the
semiconductor devices semiconductor package 200, thePFC circuit 300, thepower supply apparatus 400, and theamplifier 500 described in the sixth to ninth embodiments) may be installed in various electronic appliances. As examples, it is possible to install the electronic devices in various electronic appliances such as a computer (a personal computer, super computer, server, or the like), a smartphone, a mobile phone, a tablet, a sensor, a camera, audio equipment, a measuring apparatus, a testing apparatus, and a manufacturing apparatus. - A semiconductor device where the generation of parasitic capacitance due to an insulating layer is suppressed is realized. An electronic device equipped with this semiconductor device is also realized.
- All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
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